Squamous Transformation of Prostate Adenocarcinoma: A Report of Two Cases With Genomic Profiling

Mixed Adenosquamous Cell Carcinoma of the Prostate with Paired Sequencing on the Primary and Liver Metastasis

This report aims to shed light on the intricate challenges encountered during the diagnosis and treatment of an uncommon variant of prostate cancer-mixed adenosquamous cell carcinoma of the prostate. Prostate cancers of this nature pose distinctive diagnostic and therapeutic dilemmas due to their rarity and complex histological composition. We present a case of a 63-year-old man with metastatic prostate cancer, featuring adenocarcinoma with squamous cell differentiation, who underwent a multimodal treatment approach. The patient responded to first-line carboplatin, docetaxel, and androgen deprivation therapy, followed by androgen receptor pathway inhibitor (ARPI) maintenance. However, disease progression led to radiation therapy and a subsequent switch to Lutetium (177Lu) vipivotide tetraxetan after chemotherapy challenges. Comprehensive genetic profiling revealed shared mutations in the prostate and liver lesions, emphasizing the role of targeted therapies. Prostate-specific membrane antigen (PSMA)-targeted therapy resulted in a notable PSA decline. This case highlights the evolving treatment landscape for rare prostate cancers, integrating genetic insights for tailored interventions. In conclusion, squamous cell carcinoma (SCC) of the prostate is rare, emphasizing the imperative for enhanced comprehension in diagnosis and management. Our case suggests the potential efficacy of ARPI and PSMA-targeted therapies. Our findings advocate for a more nuanced approach to the management of this rare prostate cancer variant, leveraging genomic insights for personalized treatment strategies. This exploration serves as a foundation for further research and clinical considerations in addressing the challenges posed by mixed adenosquamous cell carcinoma of the prostate.

Case report: Squamous cell carcinoma of the prostate-a clinicopathological and genomic sequencing-based investigation

Squamous differentiation of prostate cancer, which accounts for less than 1% of all cases, is typically associated with androgen deprivation treatment (ADT) or radiotherapy. This entity is aggressive and exhibits poor prognosis due to limited response to traditional treatment. However, the underlying molecular mechanisms and etiology are not fully understood. Previous findings suggest that squamous cell differentiation may potentially arise from prostate adenocarcinoma (AC), but further validation is required to confirm this hypothesis. This paper presents a case of advanced prostate cancer with a combined histologic pattern, including keratinizing SCC and AC. The study utilized whole-exome sequencing (WES) data to analyze both subtypes and identified a significant overlap in driver gene mutations between them. This suggests that the two components shared a common origin of clones. These findings emphasize the importance of personalized clinical management for prostate SCC, and specific molecular findings can help optimize treatment strategies.

Histological patterns, subtypes and aspects of prostate cancer: different aspects, different outcomes

PURPOSE OF REVIEW

The most common prostatic cancers (PCa) are acinary adenocarcinomas. Histological subtypes have been variably defined. The purpose of this review is to discuss unusual histological patterns and subtypes of acinar adenocarcinoma, as well as other types of PCa and their prognostic and therapeutic relevance.

RECENT FINDINGS

The new term 'subtype' for morphologically defined tumor entities replaced the term 'variant' in the new 2022 classification of the WHO to allow for clear terminological distinction from genetic variants. The 2022 WHO classification mentions prostatic intraepithelial neoplasia (PIN)-like carcinoma, signet-cell-like adenocarcinoma, sarcomatoid carcinoma and pleomorphic-giant-cell adenocarcinoma of the prostate as true subtypes of acinary PCa. Other forms of acinary PCa are termed unusual histological patterns and include atrophic, foamy-cell, microcystic, pseudohyperplastic and mucinous patterns. Nonacinar forms of prostate cancer include other glandular PCa, the ductal adenocarcinoma and the treatment-associated neuroendocrine carcinoma, and nonglandular PCa, the adenosquamous carcinoma, the squamous cell carcinoma and the adenoid cystic (basal cell) carcinoma of the prostate.

SUMMARY

True subtypes of acinary PCa and other forms of glandular and nonglandular PCa show relevant differences in prognosis and treatment approach compared with classic acinary PCa. The relevance of unusual histological patterns mainly lies in their deceptive benign appearance and the need for pathologists to know about these entities for accurate and timely diagnosis.

Oligometastatic Squamous Cell Transformation From Metastatic Prostate Adenocarcinoma Treated With Systemic and Focal Therapy: A Case Report

Transformation to squamous cell carcinoma (SCC) after initial treatment of a primary prostate adenocarcinoma is rare and typically results in rapid treatment-refractory disease progression and death. Here, we present a case of a 70-year-old man who was initially treated with prostatectomy and radiotherapy, and later developed bone metastases. After commencing systemic therapy with androgen deprivation therapy (ADT) and apalutamide, his prostate-specific antigen (PSA) declined to undetectable levels, yet short-interval imaging demonstrated oligo-progression at T4, with biopsy specimen demonstrating pure SCC. Molecular profiling of both the primary prostate tumor and T4 demonstrated alterations in TMPRSS2-ERG, TP53, and FOXA1 confirming site of origin, with loss of RNF43 in the squamous metastasis. He was treated with stereotactic body radiation therapy to the SCC metastasis and continued on ADT and apalutamide with stable disease for a year post-radiation. This case highlights the importance of imaging to detect non–PSA-producing metastatic disease, the utility of radiation therapy in oligo-progression, and use of molecular profiling to provide insights into the pathogenesis of histologic transformation.

Gene fusion characterisation of rare aggressive prostate cancer variants-adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma: an analysis of 19 cases

AIMS

To evaluate the molecular underpinnings of the rare aggressive prostate cancer variants adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma.

METHODS AND RESULTS

We retrieved 19 tumours with one or more variant(s), and performed ERG immunohistochemistry, a next-generation sequencing assay targeting recurrent gene fusions, and fluorescence in-situ hybridisation (FISH) for ERG and BRAF. Divergent differentiation included: sarcomatoid carcinoma (n = 10), adenosquamous carcinoma (n = 7), and pleomorphic giant-cell carcinoma (n = 7). Five patients had more than one variant. Four had variants only in metastases. ERG rearrangement was detected in nine (47%, seven via sequencing, showing TMPRSS2-ERG fusions and one GRHL2-ERG fusion, and two via FISH, showing rearrangement via deletion). ERG was immunohistochemically positive in the adenocarcinoma in eight of nine (89%) patients, but was immunohistochemically positive in the variant in only five of nine patients (56%, typically decreased). One patient had a false-positive ERG immunohistochemical result in the sarcomatoid component despite a negative FISH result. Two (11%) harboured BRAF fusions (FAM131A-BRAF and SND1-BRAF).

CONCLUSIONS

ERG fusions are present in these rare prostate cancer variants with a frequency close to that in conventional prostate cancer (9/19, 47%). ERG immunohistochemistry usually detects rearrangement in the adenocarcinoma, but is less sensitive for the variant histology, with weak to negative staining. Adenosquamous and sarcomatoid variants can, particularly, occur together. Molecular assessment may be an additional tool in selected cases to confirm the prostatic origin of unusual tumours. The presence of two BRAF rearrangements suggests that this gene fusion may be enriched in this setting, as RAF kinase fusions have been previously reported in 1-2% of prostate cancers.

Metastatic squamous cell carcinoma transformed from prostatic adenocarcinoma following androgen deprivation therapy: A case report with clinicopathologic and molecular findings

Squamous cell carcinoma (SCC) of the prostate is a rare and clinically aggressive entity that may arise de novo or through transformation of prostatic adenocarcinoma, typically following hormonal or radiation therapy. Confirmation of prostatic origin, especially when evaluating a metastatic focus, often requires correlation with clinical and imaging findings, as the morphologic and immunohistochemical features of SCC are not organ-specific. Comprehensive genomic profiling (CGP) may provide additional information useful for confirming the primary site and for identifying potential targeted therapy options. CGP data may also contribute to our understanding of the molecular basis of squamous differentiation in prostatic malignancies. However, these data are limited, and to our knowledge, there are only three previously published cases of prostatic SCC with reported CGP findings. Herein, we report a case of metastatic keratinizing SCC diagnosed by core needle biopsy in a 68-year-old man with a history of prostatic adenocarcinoma status post radical prostatectomy and androgen deprivation therapy (ADT). NKX3.1 immunohistochemistry was negative. CGP was performed, and a TMPRSS2-ERG fusion, among other genetic alterations, was detected, supporting a diagnosis of metastatic SCC transformed from prostatic adenocarcinoma following ADT. This case supports the use of CGP or other molecular techniques not only to query potential targeted therapy options but also to refine the diagnosis and confirm the primary site of disease in cases with non-specific morphologic and immunophenotypic features, such as SCC.