Granulomatous Tumoral Melanosis Associated With Pembrolizumab Therapy: A Mimicker of Disease Progression in Metastatic Melanoma.

Immune checkpoint inhibitor therapy has revolutionized the treatment of advanced melanoma, with these agents significantly improving survival for patients with metastatic disease. With the increasing use of these agents, the number of adverse reactions secondary to their use has also increased. Sarcoidosis and sarcoid-like reactions are one such immune checkpoint inhibitor-related adverse event. We report a case of sarcoid-like granulomatous tumoral melanosis in a patient on the programmed cell death-1 (PD-1) receptor inhibitor pembrolizumab for metastatic melanoma. This is, to our knowledge, the first reported case of a sarcoidal form of tumoral melanosis in a patient on anti-PD-1 therapy. We postulate that this reflects tumor regression in response to pembrolizumab-induced immune activation, with concomitant therapy-triggered induction of a sarcoid-like reaction. These findings and the literature review presented herein should alert clinicians and pathologists to the possibility of regressed lesions with sarcoid-like features presenting as mimickers of disease progression in patients undergoing immunotherapy for advanced melanoma.

Practical Strategies to Improve the Clinical Utility of the Dermatopathology Report.

CONTEXT: -Dermatologists and subspecialty dermatopathologists, working together over many years, develop a common understanding of clinical information provided on the requisition and of terminology used in the pathology report. Challenges arise for pathologists without additional subspecialty training in dermatology/dermatopathology, and for any pathologist reporting skin biopsies for nondermatologists such as general practitioners or surgeons. OBJECTIVE: -To provide practical strategies to improve efficiency of dermatopathology sign-out, at the same time providing the clinician with clear diagnostic and prognostic information to guide patient management. DATA SOURCES: -The information outlined in this review is based on our own experiences with routine dermatopathology and dermatology practice, and review of English-language articles related to the selected topics discussed. CONCLUSIONS: -Using generic diagnoses for some benign lesions, listing pertinent negatives in the pathology report, and using logical risk management strategies when reporting on basal cell carcinoma, partial biopsies, or specimens with incomplete clinical information allow the pathologist to convey relevant and useful diagnostic information to the treating clinician.

Fibrolipomatous Hamartoma of the Nerve Arising in the Neck: A Case Report With Review of the Literature and Differential Diagnosis.

We report an unusual case of a fibrolipomatous hamartoma that arose in a nuchal nerve. Typically, fibrolipomatous hamartoma, otherwise known as a neural fibrolipoma or lipomatosis of nerve, arises in the median nerve, brachial plexus, cranial nerves, or plantar nerves. The differential diagnosis is broad and includes benign and malignant spindle cell lesions, such as spindle cell lipoma, perineurioma, and myxoid liposarcoma. We were able to identify the lesion based on the typical histology, including triphasic composition with spindle cell, neural, and adipocytic components and whorled architecture. Because of the atypical location in the neck, detailed immunohistochemical staining was performed. The lesional spindle cells were negative for SMA, CD10, CD68, EMA, S100, PGP9.5, CD34, CD56, and beta-catenin. Colloidal iron stain highlighted marked intralesional mucin deposition. This detailed immunohistochemical profile is a useful diagnostic aid and to our knowledge has not been previously described.

Utilization and utility of immunohistochemistry in dermatopathology.

Immunohistochemistry (IHC) is considered a valuable ancillary tool for dermatopathology diagnosis, but few studies have measured IHC utilization by dermatopathologists or assessed its diagnostic utility. In a regionalized, community-based dermatopathology practice, we measured IHC utilization (total requests, specific antibodies requested, and final diagnosis) over a 12-month period. Next, we assessed diagnostic utility by comparing a preliminary "pre-IHC" diagnosis based on routine histochemical staining with the final diagnosis rendered after consideration of IHC results. The dermatopathology IHC utilization rate was 1.2%, averaging 3.6 stains requested per case. Melanocytic, hematolymphoid, and fibrohistiocytic lesions made up 23%, 18%, and 16%, respectively, of the total cases requiring IHC. S100 and Melan A were the most frequently requested stains, ordered on 50% and 34% of IHC cases, respectively. The utility study revealed that IHC changed the diagnosis in 11%, confirmed a diagnosis, or excluded a differential diagnosis in 77%, and was noncontributory in 4% of cases. Where IHC results prompted a change in diagnosis, 14% were a change from a benign to malignant lesion, whereas 32% changed from one malignant entity to another. IHC is most commonly used in cutaneous melanocytic and hematolymphoid lesions. In 11% of dermatopathology cases in which IHC is used, information is provided that changes the H&E diagnosis. Such changes may have significant treatment implications. IHC is noncontributory in only a small percentage of cases.