Essentials for Pathological Evaluation of Peritoneal Surface Malignancies and Synoptic Reporting of Cytoreductive Surgery Specimens-A review and evidence-based guide

Abstract

Peritoneal surface oncology has emerged as a subspecialty of surgical oncology, with the growing popularity of surgical treatment of peritoneal metastases comprising of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Pathological evaluation plays a key role in multidisciplinary management but there are still many areas where there are no guidelines or consensus on reporting. Some tumors presenting to a peritoneal surface oncology unit are rare and pathologists my not be familiar with diagnosing and classifying those. In this manuscript, we have reviewed the evidence regarding various aspects of histopathological evaluation of peritoneal tumors. It includes establishing a diagnosis, appropriate classification and staging of common and rare tumors and evaluation of pathological response to chemotherapy. In many instances, the information captured is of prognostic value alone with no direct therapeutic implications. But proper capturing of such information is vital for generating evidence that will guide future treatment trends and research. There are no guidelines/data set for reporting cytoreductive surgery specimens. Based on the authors' experience, a format for handling/grossing and synoptic reporting of these specimens is provided.

Keywords: Cytoreductive surgery; Data set for reporting; Pathology; Surgical specimens; Synoptic reporting.

Fig. 1

Various regions of the peritoneum marked on an en-bloc total parietal peritonectomy specimen performed for serous epithelial ovarian cancer

Fig. 2

Mucinous adenocarcinoma of the colonic variety arising from the ovary

Fig. 3

Histological findings suggestive of a primary tumor arising in the GI or pancreatobiliary tract. a, b Tumor in the peritoneum. c, d Tumor in the omentum. e, f Primary tumor in the gall bladder

Fig. 4

Histological findings in the peritoneal biopsy suggestive of peritoneal mesothelioma in a patient with breast cancer

Fig. 5

CRG 3 in a patient after 3 cycles of NACT. Only site of residual disease is the ovaries. a Residual tumor in the ovary. b Chemotherapy-related changes in the ovary. c, d Chemotherapy-related changes with no residual tumor in different regions of the peritoneum

Fig. 6

Variation in the CRG in different regions of the peritoneum in the same patient. a Minimal response in tumor deposit over the sigmoid colon. b Areas showing no response. c Tumor deposit in the pouch of Douglas showing good response

Fig. 7

Low-grade mucinous appendiceal neoplasm (LAMN) tumor with low grade cytology confined to the mucosa

Fig. 8

a, b Reporting checklist for appendiceal mucinous tumors recommended by the expert panel (adapted from ref with permission)

Fig. 9

High-grade mucinous carcinoma peritonei with signet ring cells (HGMCP-S)

Fig. 10

Acellular mucin with ingrowth of blood vessels-organizing mucin (a low magnification; b high magnification)

Fig. 11

Cytological features seen in low-grade mucinous carcinoma peritonei. a Peritoneal deposit in low magnification. b Tumor deposit on the ovary with pushing invasion. c Single layer of cuboidal epithelium. d Pseudostratified columnar epithelium. e Papillary pattern. f Cribriform architecture with low grade cytological features

Fig. 12

Reporting checklist recommended by the PSOGI expert panel

Fig. 13

a Low-grade mucinous carcinoma peritonei with small focus of high-grade cytologicy. b On high power

Fig. 14

The spectrum of high-grade PMP. a, b Tumor deposits in the peritoneum showing high-grade cytology and no desmoplasia. c, d Tumor deposits in the colonic wall showing high grade cytology with infiltrative invasion

Fig. 15

Peritoneal deposits from a mucinous adenocarcinoma resembling a colorectal primary tumor but the primary site was not found. a Peritoneal deposits. b Immunohistochemistry profile suggestive of colonic origin. c Appendix showing serosal deposits with a normal mucosa

Fig. 16

Presentation of a mucinous ascites (a) with peritoneal deposits (b) and histology showing mesothelial cells with apical mucin (c)

Fig. 17

Immunohistochemistry markers for determining the primary tumor site in a patient with peritoneal metastases. ESOC epithelial serous ovarian cancer, PPSC primary peritoneal serous cancer