Pulmonary Metastasising Aneurysmal Fibrous Histiocytoma: A Case Report, Literature Review and Proposal of Standardised Diagnostic Criteria

Abstract

An aneurysmal fibrous histiocytoma is a rare cutaneous soft-tissue tumour which accounts for approximately 0.06% of all dermatopathologies. Metastasis is exceedingly uncommon, to the point that there have only been eight reported cases in the scientific literature. We present the case of a 25-year-old male with a primary aneurysmal fibrous histiocytoma located in the nuchal region which exhibited rapid growth and abrupt ulceration over a short time span and showed signs of locoregional aggressive infiltration. A subsequent histopathological analysis confirmed the presence of diffuse solid and cystic pulmonary metastases. Further genetic sequencing verified LAMTOR1-PRKCD fusion. This case report seeks to review the existing literature on aneurysmal fibrous histiocytoma, discuss the challenges of differential diagnosis and propose standardised diagnostic criteria.

Metastasizing aneurysmal dermatofibroma initially diagnosed as angiosarcoma confirmed by CD63::PRKCD fusion gene detection with nanopore sequencing

“…The combination of exons in CD63 and PRKCD is identical to that in a previous report 5 . The serine/threonine kinase domain of PRKCD and the membrane‐associated domain of CD63 were predicted to be retained, consistent with other fusion genes of DF 5–9 . Although PRKCD was included among the target genes, CD63 was not.…”

“…Most DFs harbor specific fusion genes: PDPN::PRKCB , CD63::PRKCD , LAMTOR1::PRKCD , NUMA1::SFMBT1 , and KIRREL::PRKCA (summarized in Table 1). 5–9 In particular, aneurysmal DFs are frequently driven by LAMTOR1::PRKCD fusion 7–9 . Due to the relative rarity of these fusions, split FISH is not widely used for pathological DF diagnosis.…”

“…In addition, although most DFs are benign, they rarely recur or metastasize, especially if they are large and/or have atypical histology. Specific fusion genes related to DF ( PDPN::PRKCB , CD63::PRKCD , LAMTOR1::PRKCD , NUMA1::SFMBT1 , and KIRREL::PRKCA ) have been reported 5–9 ; however, as they are rare, reverse transcription polymerase chain reaction (RT‐PCR) and fluorescence in situ hybridization (FISH) are not yet widely used for pathological diagnosis.…”