AJTCCM VOL. 29 NO. 3 2023 141
PICK OF THE PICS
A 78-year-old woman presented with unilateral pleural thickening
and intraparenchymal pulmonary nodules. e positron emission
tomography (PET) scan showed pleural and peritoneal uptake.
Clinical hypotheses included a pleural tumour inltrating the lung
or vice versa.
Microscopy of the pleural biopsy showed a malignancy with a
predominantly solid architectural pattern and in smaller proportion
papillary, composed of epithelioid cells, with scant cytoplasm and
several mitosis (Fig. 1). Immunohistochemistry showed the following
prole: CK7+; TTF1-; Napsin-; WT1+; Calretinin-; CK5/6-; D2-40-.
TTF1- and Napsin- ruled out a pulmonary origin, however, the
positivity found for WT1 should not be considered separately from
the rest of the immunohistochemistry, leading to a misdiagnosis
of mesothelioma. In fact, the results obtained from the first
immunohistochemical panel applied leads to rule out a mesothelial
nature as well (Calretinin-; CK5/6-; D2-40-).[1] Therefore, the
hypothesis of pleuropulmonary metastasis by a neoplasm with a
CK7+/WT1+ prole was raised, and attention was specically directed
toward a serous histotype.
e immunohistochemical panel was then expanded in that diagnostic
direction and the result was consistent (Fig. 2): PAX8+; CA125+;
p53+; p16+. [2-4]
Radiological/gynaecological investigation showed no uterine or
tubo-ovarian masses. e most likely hypothesis, also considering the
peritoneal wall PET uptake therefore, was a rare primary peritoneal
serous carcinoma.
1. Husain AN, Colby TV, Ordóñez NG, et al. Guidelines for Pathologic Diagnosis
of Malignant Mesothelioma 2017: Update of the Consensus Statement From the
International Mesothelioma Interest Group. Arch Pathol Lab Med 2018;142(1):89-
108. https://doi.org/10.5858/arpa.2017-0124-RA.
2. Anwar A, Kasi A. Peritoneal Cancer. 2022 Feb 24. In: StatPearls. Treasure Island (FL):
StatPearls Publishing; 2022 Jan.
3. Laury AR, Hornick JL, Perets R, et al. PAX8 reliably distinguishes ovarian serous
tumors from malignant mesothelioma. Am J Surg Pathol 2010;34(5):627-35. https://
doi.org/10.1097/PAS.0b013e3181da7687.
4. Attanoos RL, Webb R, Dojcinov SD, Gibbs AR. Value of mesothelial and epithelial
antibodies in distinguishing diuse peritoneal mesothelioma in females from serous
papillary carcinoma of the ovary and peritoneum. Histopathology 2002;40(3):237-
244. https://doi.org/10.1046/j.1365-2559.2002.01352.x.
A WT1-positive pleural neoplasm. Is it always a mesothelioma?
Diagnostic pitfall of WT1 immunohistochemistry in pleural
neoplasm
G Gaggero,1 D Taietti,2 M Concardi,3 M Mora1
1 IRCCS Ospedale Policlinico San Martino, UO Anatomia patologica ospedaliera, Genova, Italy
2 Pathology Unit, ASST del Garda, Desenzano del Garda, Brescia, Italy
3 Università di Genova, Scuola di Scienze Mediche e Farmaceutiche, Department of Integrated Surgical and Diagnostic Sciences (DISC), Division of Anatomic
Pathology, Genoa, Italy
Fig. 1 (A). Photomicrograph (histologic staining with haematoxylin-
eosin after formalin fixation and paraffin embedding of the tissue;
magnication: 10x), showing an epithelioid neoplasm (in the middle)
inltrating the pleura (on the right) and with areas of necrosis (on the
left); (B) photomicrograph (histologic staining with haematoxylin-
eosin after formalin fixation and paraffin embedding of the tissue;
magnication: 40x), showing a neoplasm with an architectural pattern
that is partly solid and partly papillary, and cytologically poorly
dierentiated and with numerous mitoses (arrows).
Fig. 2. Photomicrograph, showing the main immunohistochemical
markers useful for the diagnosis of serous carcinoma: (A) intense and
diuse cytoplasmic positivity for CK7; (B) intense and diuse nuclear
positivity for WT1; (C) intense and diuse nuclear positivity for PAX8;
(D) membrane positivity for CA125.
