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Rare But Important Diagnostic Entities II

Potpourri of Case Reports With Pitfalls and Teachable Moments

Ioffe, Olga B. MD

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doi: 10.1097/PCR.0000000000000362
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Dear readers of AJSP: Reviews and Reports,

I am delighted to present to you the first AJSP: Reviews and Reports issue of 2020. It is our new tradition to have one annual issue of the journal devoted entirely to unsolicited peer-reviewed case reports. While we continue to publish our traditional, topic-centered issues, these unsolicited case reports will be also added to the thematic issues, as well as published online. As usual, all of these will have undergone a rigorous peer and editorial review and are selected to support the educational mission of the journal. This mission has always been to promote the education of practicing pathologists and trainees and to publish materials helpful in solving significant and common diagnostic dilemmas and avoiding important pitfalls.

For this issue, we chose to focus on several areas that pose significant diagnostic challenges: difficult entities of head and neck, bone and soft tissue, histiocytic proliferations, and liver. The authors of these reports have gone to great lengths to arm us with tools and knowledge to help avoid pitfalls and make accurate diagnoses. The first group of reports is centered on head and neck pathology; it starts with an excellent, superbly organized and illustrated case series by Devins et al of two unusual human papillomavirus–related tumors of head and neck: human papillomavirus–related multiphenotypic sinonasal carcinoma and ciliated adenosquamous carcinoma. This is followed by a fascinating report of a real diagnostic pitfall: extraparotid multifocal Warthin tumor, which can mimic papillary thyroid carcinoma, well documented by Kulkarni et al. The third case report in this group, submitted by Hamza et al, describes an intraosseous carcinoma with clear cell features, which possessed chromosomal alterations of two tumors thought to be distinct: clear cell odontogenic carcinoma and mucoepidermoid carcinoma. This case highlights the sometimes unexpected results of ancillary diagnostic testing, which can open entirely new possibilities, such as a hybrid tumor, or tumors harboring translocations thought to be pathognomonic of another, distinct tumor type.

The next group of articles is devoted to bone and soft tissue pathology. The first describes another exquisite diagnostic quagmire: giant cell tumors, which can behave aggressively despite their bland appearance. This case report by Shannon et al delves into the differential diagnosis of giant cell tumors and bone sarcomas with giant cell features; this differential diagnosis is extremely difficult and made even more treacherous by sampling variation in small biopsy specimens and by obviously drastic differences in patient management that stem from these diagnoses. The second report details an unusual variant of adamantinoma with high-grade epithelial and stromal components. Because adamantinomas are usually cytologically bland, this high-grade variant may prompt a diagnosis of a metastatic sarcomatoid carcinoma. Sharifai et al address challenges and helpful diagnostic clues as well as review previous case reports of this rare variant. Next, Tanaka et al report an unusual ALK-negative inflammatory myofibroblastic tumor presenting as a small intestinal polyp in a child and harboring ETV6-NKVP3 translocation. This translocation is very rare in inflammatory myofibroblastic tumors and may cause the pathologist to question the diagnosis, especially in light of negative ALK.

The first case report devoted to histiocytic disorders is that of a congenital orbital juvenile xanthogranuloma; in addition to a nicely illustrated report, the authors review the new classification of non-Langerhans and Langerhans cell histiocytoses and discuss treatment implications of these diagnoses. Langerhans cell histiocytosis combined with Erdheim-Chester disease is described in the report of two such cases by Pires et al; their article documents this rare occurrence and describes the workup and classification of histiocytic disorders. Lastly, Langerhans cell histiocytosis presenting as unusual isolated liver involvement and subsequent recurrence in the liver transplant is reported by Rush et al. These reports raise our awareness of these subtle lesions and offer valuable teachable moments in regard to their diagnosis and workup.

Liver pathology is the theme of the next group of articles; the first describes very subtle and easily missed hepatocellular carcinoma mimicking cirrhosis in the setting of a liver explant. This report, superbly illustrated by Gosse and Appelman, alerts pathologists to this unexpected and subtle malignancy. The second report is devoted to mass-forming hepatic extramedullary hematopoiesis and includes a summary of all heretofore reported cases.

The issue is concluded by a report detailing spironolactone bodies—a finding in renal aldosteronomas in patients receiving spironolactone. This curious and pathognomonic phenomenon is well described and includes recommendations on the workup of suspected aldosteronomas.

As the goal of our journal has always been to promote the education of practicing pathologists and trainees, we attempted to select articles, which would raise awareness of rare entities, unusual presentations, and important pitfalls. We hope that this issue achieved its goal and that you will have learned new information useful in your practice or training.

© 2020 Lippincott Williams & Wilkins, Inc.