Collision tumors of the thyroid. A special clinical and pathological entity

Thyroid collision tumors are rare entities that designate two histologically and morphologically distinct tumors that occur simultaneously or as metastases from other organs within the thyroid. Medullary and papillary carcinoma co-occurrence is the most frequent. Several theories tried to explain the pathogenic mechanisms underlining collision tumors, including the theory which assumes that one tumor predisposes the other, stem cell theory, and random effect theory, but their combination better explains the origin of these tumors. Hypotheses about common genetic behavior responsible for the pathogenesis have also been suggested, such as the involvement of germline mutation of RET (Rearranged during Transfection) proto-oncogene in medullary thyroid carcinoma and papillary thyroid carcinoma coexistence, but there is controversy on this topic. Management of thyroid collision tumors is challenging owing to the presence of two distinct tumors with different biological aggressiveness, treatments options, and prognosis, and needs to be individualized.

Four-Cell Population Collision Tumor of the Scalp: A Case Report and Review of Literature

Background: Most cases of collision tumors (CTum) usually present with 2 histologic cell types. We report a unique CTum case comprised of 4 cell populations. Additionally, we performed a systematic review of the current literature published on head and neck collision tumors (HNCTum). Methods: Eighty-one-year-old male presents with a scalp lesion of several years’ duration. PET/CT scan demonstrated increased uptake in the scalp. Wide local excision with free flap reconstruction was performed and tissue pathology reviewed. Database search of HNCTum was performed and reported. Results: Specimen histopathology consisted of melanoma, squamous cell carcinoma, basal cell carcinoma, and pleomorphic dermal sarcoma. Thirty-one articles met inclusion criteria: 11 thyroid, 7 cutaneous, 7 laryngeal, 2 lymph nodes, 2 salivary gland, 1 glottic, 1 maxillary sinus, and 1 tonsil. Conclusion: We present a highly unique CTum case of 4 different cell populations. The systematic review provides a comprehensive report of HNCTum in literature.

Collision Cutaneous Neoplasms Consisting of Melanoma and Basal Cell Carcinoma

Collision tumors are defined as two histologically different tumor types that arise at the same anatomical location. According to the literature review performed, there are reports of 27 cases of collision tumors involving lentigo maligna melanoma (LMM) in-situ and basal cell carcinoma (BCC). In the absence of melanocytic extension beyond the lamina propria of the BCC compartment, mixed tumors are considered as melanoma in-situ colonizing the BCC, rather than invasive melanomas. We report an uncommon case of collision of BCC with LMM, two primary skin tumors that are seen in patients with significant sunlight exposure. In our case, the patient is a 91-year-old male presented with a translucent plaque with areas of brown pigmentation on his left lateral canthus. He had a history of multiple BCCs, squamous cell carcinomas and an invasive melanoma of right cheek. Given the clinical impression of BCC, the lesion was curetted. Histological examination demonstrated melanoma in-situ heavily infiltrating the dermal nodules of BCC. Deposits of melanin pigment were scattered throughout the tumor. The BCC contained about 50% atypical melanocytes. Further immunohistochemical evaluation with melanocytic and epithelial markers (melanin A, SOX-10, pan-cytokeratin and p63) confirmed the diagnosis. An unequivocal independent invasive melanoma component was not identified in this material. The collision of BCC and LMM is very rare. However, given the sun-damaged changes promote both tumors, their development at the same site, although unexpected, can be explained. Since the prognosis of the two entities is independent, wider excision to exclude invasive malignant melanoma is indicated.

A Wolf in Sheep’s Clothing: Collision of Melanoma and Keratoacanthoma

Collision tumors consisting of melanoma and squamous cell carcinoma are very rare. We present the case of a deceptive hyperkeratotic nodule on the forearm of a 72-year-old woman, which clinically appeared to be a squamous cell carcinoma, keratoacanthoma type. Histological examination surprisingly revealed a coexisting epithelioid melanoma. Thus, this case report shows the importance of an early histopathological and immunohistochemical workup to prevent unnecessary diagnostic and therapeutic delay with negative effects on prognosis.

Next-generation sequencing reveals novel mutations in a collision tumor of glioblastoma and meningioma

Primary intracranial collision tumors are rare in patients without predisposing factors. We report such a case in a 42-year-old female who presented with headaches and altered mental status. Imaging revealed a single heterogeneous, rim-enhancing lesion in the left parieto-occipital periventricular region, involving the corpus callosum. Stereotactic biopsy demonstrated glioblastoma. Subsequent tumor resection showed histologic evidence of glioblastoma and meningioma. Next-generation sequencing was performed on both tumor components. The glioblastoma exhibited a CDKN2A homozygous deletion and novel missense mutations in TAF1L and CSMD3, while no definitive genetic alterations were identified in the meningioma. Next-generation sequencing may yield insight into molecular drivers of intracranial collision tumors and aid in identifying future therapeutic targets.

A Potential Concomitant Sellar Embryonic Remnant-Associated Collision Tumor: Systematic Review

BackgroundDiagnosing the well-known concomitant Rathke’s cleft cyst (RCC) and differentiating it from other sellar lesions are difficult because RCC is and other sellar lesions are closely related and represent a continuum from simple RCCs to more complex lesions. The purpose of this study is to better understand the adeno- and neurohypophysis adjacent to the par intermedia remnants and their role in the origin of the coexistence of these two distinct tumor neoplasias; to assess the incidence in different age groups; to categorize the pathohistological subtype, which can be incorporated in predictive/prognostic models; and finally, to evaluate the current evidence on collision tumors of the sellar embryonic remnant tract in terms of their biological behavior and pathology.MethodsUtilizing the PubMed database, data were collected from 1920 to 2019. Information about demographics, clinical characteristics, and age was summarized and analyzed by using univariable and multivariable models. The same cell type was observed regardless of whether the tumor was only one type or mixed types, and their histologic patterns were assessed.ResultsThe incidence rates were similar among patients stratified into three age subgroups: 40–49 years (24.57%), 50–59 years (19.54%), and older than 60 years (22.98%). We found that various types of sellar lesions, namely, squamous metaplasia (SM) + goblet cells (GC) (HR 46.326), foamy macrophages (FM) (HR 39.625), epithelial cells and multinucleated giant cells or cholesterin (EM) (HR 13.195), a cavernous portion of the right internal carotid artery (CP-ICA) (HR 9.427), epithelial cells with ciliated cuboidal (EC-CC) (HR 8.456), were independently associated with RCC pathological status. These divergent AUCs (0.848 for Hypo as RCC, 0.981 for RCC co PA, 0.926 for CD and CP co RCC) and subtypes of PA (HR 4.415, HR 2.286), Hypo (HR 3.310), CD and CP (HR 2.467), EC and DC and PG and SGR (HR 1.068), coexisting with the risk of a comorbid RCC lesion, may reflect the etiologic heterogeneity of coderivation and the different effects of some risk factors on tumor subtypes. Our analyses suggested that the greatest accuracy was observed for the pituitary adenoma subtype, with an AUC of 0.981 (95% confidence interval [CI]: 0.959–1.005), while the poorest accuracy was observed for aneurysms, with an AUC of 0.531 (95% CI: 0.104–0.958). We separately analyzed and confirmed the above results. Sensitivity analysis revealed no evidence of systematic bias due to missing data.ConclusionThis study showed that the histopathological changes in patients with sellar embryonic remnant-associated collision tumors showed highly consistent epithelial cell replacement (renewal) (ciliated columnar epithelium to ciliated squamous epithelium to squamous epithelium) or accumulation, and the RCC cyst wall was similar in structure to the tracheobronchial airway epithelium, with progenitor cell characteristics. The collision accuracy between RCC and other tumors (PAs, craniopharyngioma, chordoma, etc.) is different; these characteristics constitute the theoretical basis for the postmigration development of the pharyngeal bursa.

The Usefulness of Dermoscopy for the Recognition of Malignant Collision Tumors

<b><i>Background:</i></b> Preoperative diagnosis of malignant collision tumors (MCT) is extremely difficult. The value of dermoscopy to improve the correct detection of these tumors has not been previously studied. This study aims to evaluate the diagnostic accuracy of MCT with and without dermoscopy and to describe the dermoscopic features of a large series of MCT. <b><i>Methods:</i></b> Dermoscopic images of 161 MCT were evaluated. Clinical and dermoscopic images of histopathologically proven MCT intermingled with other tumors were randomly presented to clinicians with different levels of experience, blinded to the diagnosis and objective of the study. The clinical and dermoscopic diagnostic accuracies were measured separately. <b><i>Results:</i></b> A total of 161 histopathologically proven cases of MCT were collected. The most frequent MCT was basal cell carcinoma-seborrheic keratosis collision tumor (CT; 37.9%), followed by basal cell carcinoma-melanocytic nevus CT (19.9%), and melanoma-seborrheic keratosis CT (6.8%). Diagnostic accuracy among experts on dermoscopy was 71.4%. The study included 119 participants. The percentage of correct diagnoses was 8% by naked eye examination and 36.4% by dermoscopy (<i>p</i> &#x3c; 0.001). The presence of the malignant component in the cases of MCT was not recognizable in 19.1% of cases by naked eye examination and in 11.8% of cases by dermoscopy (<i>p</i> &#x3c; 0.001). <b><i>Conclusions:</i></b> The diagnosis of MCT can be assisted and clarified by dermoscopy. However, many of these lesions manifest complex morphologies and continue to be challenging, even for experts on dermoscopy. Atypical, uncertain, or non-classifiable lesions still need a complete excision for the final diagnosis.