       NOTE: This disposition is nonprecedential.

  United States Court of Appeals
      for the Federal Circuit
              __________________________

         JOHN LARRY SANDERS AND
    SPECIALTY FERTILIZER PRODUCTS, LLC,
              Plaintiffs-Appellants,
                           v.
     THE MOSAIC COMPANY, CARGILL, INC.,
       AND CARGILL FERTILIZER, INC.,
             Defendants-Appellees.
              __________________________

                      2010-1418
              __________________________

   Appeal from the United States District Court for the
Western District of Missouri in Case No. 09-CV-0016,
Magistrate Judge John T. Maughmer.
             ___________________________

                Decided: April 20, 2011
             ___________________________

   JOHN M. COLLINS, Hovey Williams LLP, of Overland
Park, Kansas, argued for plaintiffs-appellants. With him
on the brief were SCOTT R. BROWN and MATTHEW B.
WALTERS.

   PETER M. LANCASTER, Dorsey & Whitney LLP, of
Minneapolis, Minnesota, argued for defendants-appellees.
SANDERS   v. MOSAIC COMPANY                               2


With him on the brief were DEVAN V. PADMANABHAN and
HEATHER D. REDMOND. Of counsel was J. DAVID
WHARTON, Stinson Morrison Hecker LLP, of Kansas City,
Missouri.
             __________________________

   Before PROST, SCHALL, and MOORE, Circuit Judges.
MOORE, Circuit Judge.
    John Larry Sanders and Specialty Fertilizer Products,
LLC (Sanders) appeal a stipulated judgment of nonin-
fringement of United States Patent No. 6,210,459 (’459
patent) by The Mosaic Company, Cargill, Inc., and Cargill
Fertilizer, Inc. (collectively Mosaic). Because the district
court incorrectly construed the claims of the ’459 patent,
we vacate and remand for further proceedings. Because
Mosaic’s pleadings were sufficient to allege a case of
inequitable conduct, we hold that the trial court did not
err by allowing Mosaic to amend its complaint to add a
counterclaim of inequitable conduct.
                       BACKGROUND
    This appeal comes in a suit brought by Sanders accus-
ing Mosaic of infringing various claims of the ’459 patent.
The ’459 patent is a continuation of United States patent
application 09/162,103, which issued as United States
Patent No. 6,132,485 (parent patent). The ’459 patent is
generally directed to soil nutrient compositions and
methods of using those soil nutrient compositions.
    During the litigation between Sanders and Mosaic,
the parties stipulated that the terms “soil nutrient com-
position” and “composite comprising a self-sustaining
body” should be construed in the same way. The district
court considered these claim terms within the language of
the claims, namely “soil nutrient composition compris-
3                               SANDERS   v. MOSAIC COMPANY


ing . . . a micronutrient” and “composite comprising . . . a
micronutrient.” In a claim construction order dated May
17, 2010, the court held that these terms meant “high-
concentration micronutrient compositions and compos-
ites.” The court further refined this construction based on
testimony from the parties’ experts, and held that “the
patentee disclaimed and disavowed micronutrient per-
centages lower than about five percent” during prosecu-
tion of the parent patent.
    The court also construed the same two terms, “soil nu-
trient composition” and “composite comprising a self-
sustaining body,” as “limited to non-stratified homoge-
nous products.” Again, the court held that the patentee
“disavowed fertilizer structures that were not non-
stratified homogenous products” based on a disclaimer in
the parent patent prosecution. The court also found that
“the process described in the ’459 patent would result in a
non-stratified, homogenous product,” which further
“corroborate[d] the conclusion that the disclaimers . . .
made by the patentee in connection with the ’485 parent
patent are also applicable to the patent-in-suit.”
    Subsequently, the district court granted Mosaic leave
to amend its pleadings to include a declaratory judgment
counterclaim of unenforceability due to inequitable con-
duct. The court considered the standard we articulated in
Exergen Corp. v. Wal-Mart Stores, Inc., 575 F.3d 1312
(Fed. Cir. 2009), which requires an inequitable conduct
pleading to meet the standard of Federal Rule of Civil
Procedure 9(b). After analyzing Mosaic’s pleadings, the
court noted that “the question of futility is somewhat
close,” but nevertheless granted leave to amend since the
pleadings adequately set forth the “who, what, when,
where, and how” of the alleged inequitable conduct.
SANDERS   v. MOSAIC COMPANY                              4


    The parties stipulated to noninfringement under the
court’s claim construction. The district court entered a
final judgment on June 11, 2010. Sanders appeals. We
have jurisdiction pursuant to 28 U.S.C. §1295(a)(1).
                       DISCUSSION
                              I
    We construe a patent claim according to the plain
meaning of its terms to one of ordinary skill in the rele-
vant art. Phillips v. AWH Corp., 415 F.3d 1303, 1313
(Fed. Cir. 2005) (en banc). A patentee, however, may
diverge from the plain meaning of a term by acting as its
own lexicographer. Id. at 1316. A patentee can also
narrow the meaning of a claim term through prosecution,
for example by distinguishing a claim from a piece of prior
art. Omega Eng’g, Inc. v. Raytek Corp., 334 F.3d 1314,
1323-26 (Fed. Cir. 2003). Any disclaimer, however, must
be clear and unmistakable. Id. at 1325-26.
    The district court held that Sanders disclaimed every-
thing except high-nutrient compositions in order to dis-
tinguish United States Patent No. 5,571,303 (Bexton).
The first disclaimer cited by the court occurred during
prosecution of the parent patent. During prosecution,
Sanders submitted proposed amended claims to the
examiner for discussion at an examiner interview. At the
interview, the examiner cited Bexton for the first time, as
the nearest prior art. Sanders sought to distinguish
Bexton by adding a high-concentration limitation, “said
amount of micronutrient being a majority of the composi-
tion on a weight basis.” Sanders argued that Bexton no
longer reads on the claims (in the parent) because Bexton
does not suggest “a high-concentration product as pres-
ently claimed,” it only discloses “a minor amount of trace
element, less than 5% by weight.” J.A. 264.
5                               SANDERS   v. MOSAIC COMPANY


    The claims in suit, however, are distinct from the
claims of the parent patent. For one, the claims in suit do
not include the high-concentration limitation—that
micronutrients make up “a majority of the composition.”
The claims in suit also differ from the parent claims
because they include a limitation that “the amount of
ammonium sulfate . . . [is] greater than the amount of
elemental sulfur . . . on a weight basis.” See, e.g.,’459
patent claim 1.
      Mosaic argues that despite the differences between
the parent claims and the ’459 claims, the ’459 claims are
also limited to high-concentration micronutrient. Mosaic
argues that during the prosecution of the application that
became the ’459 patent Sanders disclaimed anything but
high-concentration micronutrient. In remarks submitted
with a preliminary amendment, the applicant explained:
“The present invention is concerned with high-
concentration micronutrient compositions and composites
. . . .” J.A. 147. Mosaic asserts that this statement justi-
fies reading the “high-concentration micronutrient” limi-
tation into the claims because the applicant unreservedly
characterized the invention as a whole. We do not agree
that this introductory sentence amounts to a clear and
unmistakable disclaimer.
    The applicant goes on to explain the invention in
great detail over the next half-dozen pages. J.A. 147-54.
Of particular significance is the fact that Sanders dis-
cusses specific groups of claims, and explains how each is
distinguished from the relevant prior art references,
including Bexton. Sanders explains that the claims at
issue are distinguished from the prior art, including
Bexton, because “the amount of ammonium sulfate . . . [in
the composition is] greater than the amount of elemental
sulfur . . . on a weight basis.” J.A. 148-49. This distinc-
tion is consistent with the plain language of the claim,
SANDERS   v. MOSAIC COMPANY                              6


which includes no limitation on the amount of micronutri-
ent present in the composition. In contrast, in the same
remarks, Sanders went on to distinguish a different group
of claims in the ’459 patent, not at issue, from Bexton
based on the amount of micronutrient; these claims are
expressly limited to “4.62% to about 74% by weight” of
micronutrient. J.A. 150-53. Sanders’ argument with
respect to this discrete group of claims further under-
scores that he did not intend to generally distinguish his
invention from Bexton based on the micronutrient concen-
tration, notwithstanding the introductory sentence char-
acterizing “[t]he present invention.” Considering the
entirety of the remarks, we conclude that Sanders has not
clearly and unambiguously limited the claims at issue to
high-concentration compositions.
    Neither the arguments during prosecution of the ’459
patent nor the comments and amendments in the parent
prosecution clearly and unambiguously limit the scope of
the claims at issue. As a result, we conclude that prosecu-
tion disclaimer does not limit the claims at issue to high-
concentration micronutrient compositions.
    The trial court also limited the claims at issue to
“non-stratified homogenous products” based on (1) state-
ments made in the parent prosecution and (2) the trial
court’s understanding that the process described in the
’459 patent specification would result in a non-stratified
homogenous product. During the parent prosecution,
Sanders characterized a prior art reference as describing
“a stratified, non-homogenous fertilizer product” in an
examiner interview. J.A. 264. At the time, some of
Sanders’s proposed claims were expressly limited to a
“composition comprising a substantially homogenious [sic]
mixture” of ingredients, which distinguished them from
the prior art. J.A. 257. The claims at issue, however, are
not limited to homogenous mixtures. Likewise, the speci-
7                               SANDERS   v. MOSAIC COMPANY


fication does not indicate that the invention is limited
solely to homogenous mixtures. As a result, we hold that
Sanders did not clearly disclaim soil compositions other
than non-stratified homogenous products.
     Turning now to the construction of the terms at issue,
the parties agreed that “soil nutrient composition” and a
“composite comprising a self-sustaining body,” both “com-
prising . . . a micronutrient,” should be construed the
same way. Because we find the specification, prosecution
history, and language of the claims do not limit these
terms solely to high-concentration micronutrient composi-
tions, and do not exclude compositions other than non-
stratified homogenous products, we decline to read those
limitations into the plain language of the claim. Instead,
“comprising . . . a micronutrient” should be given its plain
meaning, which is “including, but not limited to, . . . a
micronutrient.” See CIAS, Inc. v. Alliance Gaming Corp.,
504 F.3d 1356, 1360 (Fed. Cir. 2007) (“In the patent claim
context the term ‘comprising’ is well understood to mean
‘including but not limited to.’”).
    The parties also contest the construction of the term
“mixture.” The trial court construed mixture as part of a
larger phrase: “composite comprising a self-sustaining
body formed of a mixture comprising ammonium sulfate,
elemental sulfur, and a micronutrient selected from” a
group of micronutrients. The court held that “mixture”
within this phrase meant “a mixture of those listed ele-
ments: ammonium sulfate, elemental sulfur, and at least
one micronutrient.” Thus, it appears the court construed
“mixture” to mean “a mixture.” We agree that “mixture”
does not require any additional construction. We note,
however, that the phrase construed by the trial court is
actually “a mixture comprising” various ingredients.
While the claimed mixture must include the listed ingre-
dients, it is not limited to them, and may optionally
SANDERS   v. MOSAIC COMPANY                                  8


include other components in addition to those explicitly
recited. CIAS, 504 F.3d at 1360-61.
                              II
    Sanders also appeals the district court’s grant of Mo-
saic’s motion for leave to amend its pleadings to add
allegations of inequitable conduct. A motion to amend a
pleading is a procedural matter governed by the law of
the regional circuit. Exergen Corp. v. Wal-Mart Stores,
Inc., 575 F.3d 1312, 1318 (Fed. Cir. 2009). “Whether
inequitable conduct has been pleaded with particularity
under Rule 9(b) is a question governed by Federal Circuit
law.” Id. To plead inequitable conduct, “the pleading
must identify the specific who, what, when, where, and
how of the material misrepresentation or omission com-
mitted before the PTO.” Id. at 1328. At the pleading
stage the proponent of the inequitable conduct theory
need only plead facts supporting a reasonable inference
that a specific individual knew of the misrepresentation
and had the specific intent to deceive the PTO. Id. at
1328-29. “A reasonable inference is one that is plausible
and that flows logically from the facts alleged . . . .” Id. at
1329 n.5.
    The court below conducted a thorough analysis of Mo-
saic’s amended pleadings in light of the standard we set
forth in Exergen. Although the court specifically noted
that “it remains to be seen whether the inequitable con-
duct claim . . . will survive a motion for summary judg-
ment,” it concluded that Mosaic alleged facts sufficient to
meet the pleading standard. We agree.
    Sanders argues that the amended pleading does not
include any allegations of knowledge or specific intent to
deceive, and is futile in any case. Mosaic’s amended
counterclaims, however, plead facts from which the court
could reasonably infer both knowledge and intent to
9                               SANDERS   v. MOSAIC COMPANY


deceive the Patent Office. For example, Mosaic’s Second
Amended Counterclaim alleges that Sanders filed a
continuation application and included an expert declara-
tion from Dr. Larry S. Murphy that was written in signifi-
cant part by an employee of co-plaintiff Specialty
Fertilizers. Mosaic also alleges that Sanders failed to
disclose Dr. Murphy’s business relationship with Sanders
and his company, and that Dr. Murphy omitted publica-
tions that he co-authored with Sanders on the curriculum
vitae submitted to the Patent Office. Mosaic further
alleges that the failure to disclose the relationship be-
tween Dr. Murphy and Sanders was intentional and
material.
    Our cases indicate that the failure to disclose an ex-
pert’s affiliation with the applicant to the Patent Office
can constitute inequitable conduct. See, e.g., Refac Int’l,
Ltd. v. Lotus Dev. Corp., 81 F.3d 1576, 1584-85 (Fed. Cir.
1996). It is a plausible inference, flowing logically from
the facts alleged, that the applicant intended to conceal
Dr. Murphy’s connection to Sanders and Specialty Fertil-
izers from the Patent Office, thereby buttressing his
credibility as an impartial witness. We see no error in the
court’s Exergen analysis, and Sanders’s other arguments
on this issue are likewise unavailing. As a result, we hold
that the trial court did not err by allowing Mosaic to
amend its complaint to add a counterclaim of inequitable
conduct. Consequently, on remand, Mosaic's counterclaim
will be before the court for adjudication.
                VACATED and REMANDED
                             COSTS
    No costs.
