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Rare but important diagnostic entities: potpourri of case reports with teachable moments

Ioffe, Olga B. MD

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doi: 10.1097/PCR.0000000000000288
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Dear readers of AJSP:Reviews and Reports,

I would like to present to you the second issue of the journal devoted entirely to unsolicited peer-reviewed case reports submitted to the American Journal of Surgical Pathology. As I have informed you last year, we intend to continue publishing our traditional, topic-centered issues of the journal, along with occasional issues devoted exclusively to these unsolicited case reports. The 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 were selected to support the educational mission of our journal.

The issue is kicked off by a very timely and eloquent letter to the editor, penned by U. Balis and colleagues. It discusses the benefits of whole slide imaging used for slide storage, and makes a very compelling case that whole slide imaging is not only the way to savings, but also to progress in research.

The case reports selected for this issue represent an eclectic collection illustrating unusual entities and difficult diagnostic dilemmas. The authors of these reports have gone to great lengths to educate and arm us with tools and knowledge to avoid pitfalls and make accurate diagnoses. The first two case reports deal with rare lymphoproliferative disorders: Poklepovicz et al describe a case of follicular dendritic cell sarcoma and highlight the difficulties encountered when making this diagnosis on limited samples such as fine needle aspiration specimens; this report also documents autopsy findings in an advanced case of this rare tumor, as well as an unusual pathogenic mutation in NF2 gene. The second report, by Katsushima et al, provides a detailed description of a composite lymphoma with rare components, along with the definition and permutations of this rare condition, as well as a thorough literature analysis of similar cases.

The next three articles deal with rare conditions of the gastrointestinal tract. Altawari and co-authors report a case of brown bowel syndrome, presenting in their patient with malabsoprtion and small bowel obstruction necessitating surgical bowel resection. The report highlights the various and subtle presentations of this disease, diagnostic difficulties presented by routine superficial endoscopic biopsies, and the importance of rendering a correct and timely diagnosis. Next, K. Shaffique et al provide a nicely documented case report of a rare mixed acinar and neuroendocrine carcinoma arising in a highly unusual location - common bile duct. The third case report illustrates a rare lesion, pulse granuloma, which is usually located in intestinal fistulas but in this case was seen in a highly unusual location - mesenteric lymph node – and in association with inflammatory bowel disease complicated by adenocarcinoma – also an extremely rare occurrence for what is essentially an inflammatory reaction to legumes.

Pulmonary pathology is the theme for the next two articles. The first is a well illustrated report of rare lung neoplasm, called ciliated muconodular papillary tumor, by Baratelli et al. These tumors are exquisitely difficult to diagnose, especially in small specimens, due to their low-grade cytomorphology and presence of cilia, the latter usually considered a sign of non-neoplastic proliferation. Lung biopsies from immunocompromised patients always engender a whole host of differential diagnostic considerations; M. Mehrad and colleagues add to this list by describing a novel and diagnostically challenging condition of Polyomavirus-associated lymphocytic bronchitis/bronchiolitis documented in both native and allograft lung biopsies. The authors conclude that this process needs to be ruled out when allograft rejection is considered; in addition, viral cytopathic changes and concurrent squamous metaplasia can mimic a neoplastic or dysplastic proliferation.

The next stop on this wild ride through unusual entities is genitourinary tract. J. Hibbert and co-authors provide a great description of a rare subtype of renal carcinoma – renal cell carcinoma with (angio) leiomyomatous stroma-in a patient with tuberous sclerosis complex, also manifested by multiple angiomyolipomas of the same kidney. This tumor is considered to be an indolent subtype of clear cell carcinoma with a distinct morphology that, when encountered, should prompt genetic work-up for tuberous sclerosis. Another rare renal tumor - well differentiated neuroendocrine tumor - is reported by V. Manucha et al; primary renal neuroendocrine tumors are very rare, and the authors discuss features used to categorize these neoplasms. Finally, Saleem et al present a case of clear cell carcinoma of the urinary bladder in an immunocompromised pediatric patient; while primary clear cell carcinoma of the bladder is very rare, the fascinating aspect of this report is that the tumor appears to harbor polyomavirus, raising the possibility of oncogenic viral carcinogenesis – at least in this case, and possibly in general.

The issue is concluded by two case reports of rare soft tissue and bone tumors. K. Homlar and colleagues provide a detailed clinical and pathologic description of phosphaturic mesenchymal tumor causing osteomalacia. The authors raise awareness of this easily treatable condition, which can result in catastrophic complications but notoriously eludes diagnosis for years due to non-specific clinical presentation. The last case is an unusual variant of chordoma – anaplastic chordoma, presenting at an unusually early age and in an unusual location. D. Morbeck and co-authors describe the differential diagnosis specific to this age group, and the unique molecular alterations of this chordoma variant.

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.

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