KRAS 117N positive Rosai-Dorfman disease with atypical features.

Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is a rare disease typically characterized by a histiocytic proliferation within lymph nodes, which is due to an unknown etiology. Extranodal involvement can occur, and it more rarely can involve the skin. RDD generally presents with an indolent nature and follows a benign disease course, although more aggressive cases have been reported. The condition predominately affects children and young adults. It is classically characterized by massive, bilateral painless lymphadenopathy and accumulation of CD68-positive, S100-positive, CD1a-negative histiocytes, with the presence of emperipolesis as a hallmark. Herein, we present an aggressive case in a 76-year-old male with past medical history significant for prostate cancer, who presented with a 7-month history of lymphadenopathy and new onset of multiple large abdominal wall, cutaneous, lymph node, liver, and lung masses, all of which were histopathologically atypical, but showed features consistent with RDD, including emperipolesis and strong S100 positivity. Molecular studies showed a KRAS 117N mutation, which has been recently reported in RDD. While most cases present as a benign tumor, this case demonstrated aggressive features clinically, showed partial response to MEK inhibitor immunotherapy in the setting of a KRAS mutation, and demonstrated atypical cytologic features on histopathology.

Scalp psoriasis with increased hair density.

Psoriasis is a chronic autoimmune skin disease that commonly affects the scalp. Psoriatic lesions on the scalp typically result in alopecia, possibly due to a higher proportion of hairs in the catagen and telogen stages. Involvement of the scalp in psoriasis can be problematic for the patient's quality of life as well as the clinician treating the condition. Here, we present an unusual case of scalp psoriasis presenting with increased hair density in the involved area that was resistant to topical steroids.

A rare case of cutaneous oncocytic hidradenoma.

Oncocytes are epithelial cells characterized by their abundant eosinophilic and finely granular cytoplasm. Their histologic appearance is due to excessive amounts of cytoplasmic mitochondria. Oncocytes generally occur in the setting of benign neoplasms. Oncocytomas, or tumors composed primarily of oncocytes, are typically found in the kidneys. Other common sites include the salivary, thyroid, and parathyroid glands. Oncocytic metaplasia has only been rarely reported in various cutaneous neoplasms. We report a case of an elderly male presenting with a 5 mm erythematous papule on his left scalp, who underwent a shave biopsy showing a nodular, dermal-based adnexal tumor with prominent ductal differentiation, composed of multiple small, well-formed lumina surrounded by enlarged and bland-appearing epithelioid cells. Cytokeratin 7 (CK7), epithelial membrane antigen (EMA) and monoclonal carcinoembryonic antigen (mCEA) immunohistochemical stains were positive, consistent with adnexal differentiation. Phosphotungstic acid-hematoxylin (PTAH) and Luxol fast blue (LFB) stains highlighted the cytoplasmic granules, consistent with mitochondria. The overall findings were consistent with an oncocytic nodular hidradenoma. Oncocytic hidradenoma is a very rare entity, with only 1 previously reported case in the literature.

The risk of melanoma and hematologic cancers in patients with psoriasis.

BACKGROUND: The risk of melanoma and hematologic cancers in patients with psoriasis is controversial. OBJECTIVE: We sought to assess the risk of melanoma and hematologic cancers in patients with psoriasis, and the association with different treatments. METHODS: We used case-control and retrospective cohort designs to determine melanoma or hematologic cancer risk in patients with psoriasis. Risk with treatment type was assessed using Fisher exact test. RESULTS: Patients with psoriasis had 1.53 times greater risk of developing a malignancy compared with patients without psoriasis (P < .01). There were no significant differences in malignancy risk among patients treated with topicals, phototherapy, systemics, or biologic agents. Patients with psoriasis and malignancy did not have significantly worse survival than patients without psoriasis. LIMITATIONS: It is possible that patients developed malignancy subsequent to the follow-up time included in the study. CONCLUSION: Patients with psoriasis may experience an elevated risk of melanoma and hematologic cancers, compared with the general population. The risk is not increased by systemic or biologic psoriasis therapies.

Oral ponesimod for psoriasis compared to other investigational therapies.

Oral ponesimod is a new therapy for the treatment of moderate-to-severe plaque psoriasis. Vaclavkova et al conducted a phase 2 trial that demonstrated moderate efficacy of ponesimod in the treatment of psoriasis. Here we discuss various biologic agents with alternative mechanisms of action, that have demonstrated superior efficacy in psoriasis, and call into question the risks versus benefits of ponesimod therapy.