Anatomic pathology selected abstracts

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Editors: Rouzan Karabakhtsian, MD, PhD, professor of pathology and director of the Women’s Health Pathology Fellowship, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY; Shaomin Hu, MD, PhD, staff pathologist, Cleveland Clinic; S. Emily Bachert, MD, breast pathology fellow, Brigham and Women’s Hospital, Boston; and Amarpreet Bhalla, MD, assistant professor of pathology, Albert Einstein College of Medicine, Montefiore Medical Center.

High-grade appendiceal mucinous neoplasm: clinicopathologic findings

July 2023—High-grade appendiceal mucinous neoplasm is a relatively recent term that describes a rare epithelial neoplasm of the appendix that demonstrates pushing-type invasion but high-grade cytologic atypia. Because it has been understudied, the authors conducted a multi-institutional retrospective study to describe the clinicopathologic features of high-grade appendiceal mucinous neoplasm (HAMN). They reviewed the clinical and histologic features of 35 HAMNs and the molecular features of eight of the cases. Patients were an average of 57 years old and most commonly presented with abdominal or pelvic pain. Histologically, 57 percent of the tumors showed widespread high-grade features. Architectural patterns in high-grade areas included flat, undulating, or villous growth, and, occasionally, micropapillary, cribriform, or multilayered growth. Thirteen cases had intact serosa, and the remaining 22 had perforated serosa, including seven with peritoneal acellular mucin beyond the appendiceal serosa and 10 with grade 2 pseudomyxoma peritonei. Molecular abnormalities included KRAS mutations in seven cases and TP53 mutations in four. No tumor confined to the appendix recurred. Two patients who did not have pseudomyxoma peritonei at initial presentation developed pseudomyxoma on follow-up. Among 11 patients who presented with pseudomyxoma peritonei, five died of disease and three were alive with disease at last follow-up. The authors concluded that HAMNs have a presentation similar to that of low-grade appendiceal mucinous neoplasm, as well as similar stage-based prognoses. Most HAMNs spread to the peritoneum as grade 2 pseudomyxoma peritonei, which may be associated with a worse prognosis than classic grade 1 pseudomyxoma peritonei.

Gonzalez RS, Carr NJ, Liao H, et al. High-grade appendiceal mucinous neoplasm: Clinicopathologic findings in 35 cases. Arch Pathol Lab Med. 2022;146(12):1471–1478.

Correspondence: Dr. Raul S. Gonzalez at rgonzal5@bidmc.harvard.edu

Assessment of pleomorphic liposarcoma cases with emphasis on morphologic variants

Pleomorphic liposarcoma is a highly aggressive sarcoma comprising variable numbers of pleomorphic lipoblasts mixed with undifferentiated pleomorphic sarcoma-like areas. Morphologic variants, such as myxofibrosarcoma-like or epithelioid, may cause diagnostic difficulties, especially on core biopsy. Yet data on the prognostic significance of these patterns are limited. The authors conducted a study in which 120 pleomorphic liposarcoma biopsies and resection specimens were reviewed and cataloged in 10 percent increments based on the presence of myxofibrosarcoma-like, undifferentiated pleomorphic sarcoma (UPS)-like, and epithelioid foci. The study included 75 males and 45 females ranging in age from eight to 98 years (median, 62.5 years). Cases arose in the extremities (n=72), trunk (n=32), head/neck (n=10), bone (n=4), mediastinum (n=1), or viscera (colon polyp, n=1). Of those pleomorphic liposarcomas with known depth (n=81), 40 were intramuscular, 34 were subcutaneous, and seven arose in the dermis. They ranged from 1 to 24.5 cm (median, 7 cm). Five of the 70 patients with one month or more of follow-up had recurrence and 15 had metastasis. The five-year overall survival and event-free survival rates were 66.2 percent and 63.1 percent, respectively. Patients with tumors of 5 cm or more had inferior overall survival compared with those who had tumors of less than 5 cm. The presence of epithelioid areas was also statistically significant in terms of poorer overall patient survival and event-free survival, and patients who had tumors with 50 percent or more undifferentiated pleomorphic-like areas had better overall survival. A trend towards poorer outcomes in patients who had tumors with necrosis (one percent or more) was noted. Pleomorphic liposarcoma is an aggressive adipocytic malignancy that is most commonly found in the extremities of older adults. The morphologic features of these tumors are diverse, and they may be mistaken for UPS or myxofibrosarcoma, carcinoma, and melanoma, particularly on biopsies. Tumor size, necrosis, and epithelioid morphology are associated with adverse prognosis.

Gjeorgjievski GS, Thway K, Dermawan JK, et al. Pleomorphic liposarcoma: A series of 120 cases with emphasis on morphologic variants. Am J Surg Pathol. 2022;46(12):1700–1705.

Correspondence: Dr. Karen J. Fritchie at fritchk@ccf.org