Fibrohistiocytic Tumors

USP6-Associated Neoplasms: A Rapidly Expanding Family of Lesions

Nearly 20 years ago, the first description of a translocation involving chromosome 17 on which USP6 resides was described. Since then, not only the culprit gene but also many fusion partners, leading to transcriptional activation of USP6, have been detected. The first neoplasm known to harbor USP6 rearrangements was aneurysmal bone cyst. Since then, other entities like nodular fasciitis, myositis ossificans, fibro-osseous pseudotumor of digits, and a subgroup of fibromas of tendon sheath, probably representing tenosynovial nodular fasciitis, have been added to the list of USP6-rearranged lesions. Remarkably, all of them share clinical as well as morphological characteristics, and authors have suggested that these entities actually belong to the same spectrum. This review summarizes the current knowledge regarding USP6-rearranged lesions and further elaborates on how these neoplasms relate to one another. We propose to call these lesions UAN (Usp6-associated neoplasm).

Deep benign fibrous histiocytoma occurring in the kidney: Case report

RATIONALE

Deep benign fibrous histiocytoma (BFH) is relatively rare in contrast to superficial BFH involving the skin. Moreover, it was extremely rare for deep BFH occurring in the solid organ. To our knowledge, so far, only one case of deep BFH of the kidney was reported in English literature.

PATIENT CONCERNS

Herein, we report another case of deep BFH located in the kidney in a 88-year-old female. She was referred to our hospital for a severe pain in the right upper abdomen. Computed tomography revealed a round low-density shadow measuring 6 cm in the kidney.

DIAGNOSIS

The lesion was diagnosed as a deep BFH of the kidney, as the tumor was histologically predominately composed of bland ovoid cells arranged in a storiform pattern.

INTERVENTION

The patient underwent the total resection of the right kidney with the tumor in our hospital.

OUTCOMES

The postoperative course was uneventful. The patient was alive with no tumor recurrence or metastasis within 6 months of follow-up.

LESSONS

We present another case of deep BFH of the kidney. Because of the rarity, the tumor may be poorly recognized. The typical storiform pattern in histology may be helpful for diagnosis. This report serves to remind that deep BFH is also a differential diagnosis for a tumor with storiform pattern in the kidney.

Nodular fasciitis, a forgotten entity

BACKGROUND

Nodular fasciitis is a benign pseudosarcomatous, self-limited, and reactive process. Based on its clinical and histological features - a fast-growing, solitary tumor with high cellularity and mitotic count - nodular fasciitis is considered to be a benign mimic of sarcoma.

METHODS

We present four cases of nodular fasciitis and a review of the literature.

RESULTS

The cases we present were initially misdiagnosed as sarcoma; two as dermatofibrosarcoma protuberans, one as atypical fibroxanthoma, and one as leiomyosarcoma.

CONCLUSION

Awareness of this entity among dermatologists is important as misdiagnosis may lead to unnecessary treatments associated with increased morbidity.