A 62-year-old male presented with pain and haematuria starting 3 months before. The computed tomography showed focal and mural bladder thickening with ureteropelvic dilatation. The following transurethral bladder resection revealed a high-grade muscle-invasive urothelial carcinoma. In the subsequent cystoprostatectomy we found the same tumour, but adding focal tumour-associated stromal osseous metaplasia. Ossifying metaplasia is an extremely rare feature in urothelial carcinoma, with a few reported cases and represents a diagnostic challenge, mimicking radiotherapy-induced sarcoma or sarcomatoid carcinoma.

Background. Diagnosis of dedifferentiated liposarcoma (DDL) can sometimes be challenging due to a wide variety of histological features. \"Meningothelial-like\" whorl is an uncommon histological feature of DDL, which is also observed in neural tumors and follicular dendritic cell sarcoma. This feature is frequently associated with metaplastic bone formation. We conducted this study to describe the clinicopathological features of DDL with meningothelial-like whorls that would aid in establishing accurate diagnosis. Material and Methods. Microscopic glass slides of 5 cases of DDL with meningothelial-like whorls, diagnosed between January 2010 and December 2019, were reviewed. Results. Paratesticular region was the most common site. Whorls occupied 10% to 75% of tumor area and ranged in size from <0.1 cm to >2 cm. In 1 case, these whorls coalesced to form large areas of dedifferentiation. The cells forming whorls were spindle to epithelioid shaped and lacked significant nuclear pleomorphism and increased mitoses. Metaplastic bone formation was observed in 4 cases and cartilage formation in 3 cases. p16 and α-smooth muscle actin (α-SMA) immunohistochemical stains were positive in 2 cases, when performed. MDM2 gene amplification was observed in all cases by fluorescence in situ hybridization technique. These tumors showed aggressive behavior, similar to that of DDL without meningothelial-like whorls. Two patients died, 1 developed recurrence, 1 presented as recurrent tumor, and 1 developed metastasis. Conclusion. Meningothelial-like whorls in DDL most likely represent an early stage of dedifferentiation. Presence of well-differentiated liposarcoma areas, metaplastic bone formation, positive expressions for p16 and α-SMA immunohistochemical stains, and MDM2 gene amplification are useful diagnostic clues. These tumors have the potential to behave aggressively.

Background: Osseous metaplasia is considered as a response to insults such as chronic inflammation or mucin extravasation in colorectal polyps.Case report: we report two cases of osseous metaplasia in juvenile (retention) polyps as incidental histopathological findings in a case of rectal juvenile polyposis and a patient with solitary rectal juvenile polyp.Conclusion: Osseous metaplasia can occur in colorectal juvenile polyps and is considered a probable response to mucin extravasation and/or chronic inflammation. The clinical and prognostic significance of osseous metaplasia in these polyps is unknown.

BACKGROUND: The bone formation within bladder tumors could be encountered in 3 conditions. These might consist of malignant bone formation in mesenchymal tumors; mixed mesenchymal and epithelial tumors; and epithelial tumors with stromal osseous metaplasia (SOM). This last is relatively rare. According to the English literature, only 12 cases have been reported in primary tumor and 7 in metastatic deposits of bladder primaries. Herein, we presented an additional case.
METHODS: An 83-year-old man was admitted 13 years ago for prostatic adenocarcinoma, treated with radical prostatectomy. Biochemical recurrence was detected 2 years after surgery (prostate-specific-antigen (PSA) level: 4.60 ng/mL) and progressively normalized (<1.0 ng/mL) after adjuvant radiotherapy and annual injection of leuprorelin (enantoneR). He was referred after 8 years for hematuria, PSA level having slightly increased (0.60 ng/ml). Cystoscopy showed a nodular growth in the bladder wall, visualized as a calcified tumor on computed tomography (CT) and removed with transurethral resection. Histologically, the tumor consists of a non-muscle-invasive high grade papillary urothelial carcinoma with metaplastic bone within the stroma. Immunohistochemical analysis particularly demonstrated positive expression of respectively CD56 on osteoblasts, and CD68 on osteoclasts. MDM2 and CDK4 were negatives on osteoid and bone tissue. Six courses of Bacillus Calmette-Guerin (BCG) therapy have been administered. Two local recidives have occurred during an 8-month follow-up period after immunotherapy and were treated with six further courses of BCG therapy. At one-month follow-up, the patient was well without remaining symptoms.
CONCLUSIONS: SOM is a rare benign condition whose pathogenesis remains uncompletely defined. Sarcomatoïd carcinoma represents the main differential diagnosis that influences therapeutic procedures. Prognosis depends essentially on the extent of the carcinomatous component .

Stromal ossification has been reported in relation with gastrointestinal (GI) cancers. Heterotopic ossification of benign gastric polyps with bone formation is rarely documented and sometimes associated with calcification. Thus, the presence of foci of metaplastic bone (FMB) does not always imply GI cancer.

Supraspinous ossified rods have been reported in the sacra of some derived sauropod dinosaurs. Although different hypotheses have been proposed to explain the origin of this structure, histological evidence has never been provided to support or reject any of them. In order to establish its origin, we analyse and characterize the microstructure of the supraspinous rod of two sauropod dinosaurs from the Upper Cretaceous of Argentina. The supraspinous ossified rod is almost entirely formed by dense Haversian bone. Remains of primary bone consist entirely of an avascular tissue composed of two types of fibre-like structures, which are coarse and longitudinally (parallel to the main axis of the element) oriented. These structures are differentiated on the basis of their optical properties under polarized light. Very thin fibrous strands are also observed in some regions. These small fibres are all oriented parallel to one another but perpendicular to the element main axis. Histological features of the primary bone tissue indicate that the sacral supraspinous rod corresponds to an ossified supraspinous ligament. The formation of this structure appears to have been a non-pathological metaplastic ossification, possibly induced by the continuous tensile forces applied to the element.

Diffuse pulmonary ossification (DPO) is a rare pulmonary lesion. DPO is typically detected at autopsy rather than premortem. Recently, however, several cases were diagnosed antemortem using computed tomography, high-resolution computed tomography, or video-assisted thoracic surgery. In the present study, we evaluated DPO at autopsy from two patients with post-myocardial infarction (cases 1 and 3) and one patient with duodenal cancer (case 2). Multiple metaplastic bones (nodular in case 1 and 3 or dendriform in case 2) were detected in these three cases. In an attempt to detect aluminum and iron deposition in these metaplastic bones, histochemical investigations were performed. The two nodular types of one and three cases were positive for aluminum and iron, but the dendriform type of case 2 was positive only for aluminum. The depositions occurred in a linear pattern along the calcifying front. It is of great interest that these deposition patterns were similar to those of bones from three previously reported DPO cases and from the bones of hemodialysis patients. It is suggested that these abnormal metal depositions in the calcifying front might disturb the normal mineralization processes of the metaplastic bones, although no morphological abnormality was detected, except for dense black color of calcifying front lines. Further investigations are needed in more patients with DPO to obtain more information on this topic.