Collision tumor of the thyroid: follicular variant of papillary carcinoma and squamous carcinoma

Cervical lymph node metastasis as the first symptom of combined anaplastic thyroid carcinoma (squamous cell carcinoma) and follicular carcinoma: a case report

BACKGROUND

Anaplastic thyroid carcinoma(ATC) is a rare pathological type of thyroid malignancy. Primary squamous cell carcinoma of thyroid(PSCCT) is now considered as a subtype of ATC, hereinafter referred to as ATC-SCC subtype. ATC-SCC subtype combined with follicular thyroid carcinoma is exceedingly rare, with fewer cases reported. The ATC-SCC subtype is a highly invasive tumor with a poor prognosis for patients after metastasis occurs, and current treatment of this type of tumor is tricky.

CASE PRESENTATION

A 68-year-old female patient presented with a gradually growing swelling of right cervical region. Comprehensive auxiliary examinations and postoperative pathology confirmed the diagnosis of ATC-SCC subtype with follicular thyroid carcinoma, and the metastasis squamous cell carcinoma of the right cervical lymph nodes originates from ATC-SCC subtype. The patient received chemoradiotherapy postoperative. However, the residual cervical lymph nodes metastasis with squamous cell carcinoma still infiltrated surrounding structures in the neck extensively after palliative resection. The patient died 7 months after surgery.

CONCLUSION

Our case highlights that cervical lymph node metastasis may be a significant factor in the poor prognosis of ATC-SCC subtype. This malignancy should be detected and treated early.

The coexistence of papillary thyroid carcinoma, anaplastic thyroid carcinoma (squamous cell carcinoma subtype) and poorly differentiated thyroid carcinoma: a case report

Background

Papillary thyroid carcinoma (PTC) accounts for about 60% of adult thyroid carcinoma and generally has an excellent prognosis. Primary squamous cell carcinoma of thyroid (PSCCT) is a rare thyroid tumor with high malignancy and poor prognosis. In 2022, the 5th edition of World Health Organization (WHO) has classified it as a subtype of anaplastic thyroid carcinoma (ATC), abbreviated as ATC-squamous cell carcinoma (SCC) subtype. Poorly differentiated thyroid carcinoma (PDTC) is a kind of follicular-derived malignancy, which is prone to recurrence and distant metastasis. Here, we report a rare case of the coexistence of PTC, ATC-SCC subtype and PDTC.

Case Description

We herein report a case of 69-year-old female who initially presented with a history of left neck mass for one month. Comprehensive auxiliary examinations and postoperative pathology confirmed the diagnosis of PTC combined with ATC-SCC subtype, and PDTC. Total thyroidectomy with radical left cervical lymph node dissection was performed, followed by thyroid-stimulating hormone (TSH) suppressive therapy, 131I, radiotherapy and chemotherapy. The patient showed no tumor recurrence or metastasis after a 5-month postoperative follow-up.

Conclusions

The simultaneous occurrence of PTC, ATC-SCC subtype, and PDTC is extremely rare in clinical terms or literature reports. The treatment has not been standardized, and early radical surgery is the first choice. In addition, the combination of adjuvant therapies such as TSH suppressive therapy, radiotherapy, chemotherapy and 131I may further improve the prognosis of the patient.

Collision tumor between a spinal schwannoma and chronic lymphocytic leukemia/small lymphocytic lymphoma: case report and review of the literature

A collision tumor is one where two neoplasms of differing type occur at the same anatomical site. We present a patient suffering from non Hodgkin small cell lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) and complaining intense lumbar back pain refractory to medical treatment. Lumbosacral MRI showed an intradural extramedullary lesion in the left L2-L3 foramen with extracanalar development and compression of psoas muscle. CT showed intralesional calcification. The patient underwent resection of the lesion through a paraspinal posterolateral approach (Wiltse approach). The histology was of schwannoma with intralesional calcifications and lymphocitic infiltrates compatible with B-lineage SLL/CLL. After the operation the patient suffer from left psoas muscle motor weakness (3/5 MRC). Because of hematological disease progression, she underwent 6 cycles of chemioterapy (Fludarabine, Cyclophosphamide, Rituximab). At a six-month follow-up no recurrence or residual tumor upon lumbosacral MR imaging was detectable and the left thigh flexion returned normal. To our knowledge, this is the first described case in the literature of collision tumor between a solitary spinal Schwannoma and SLL/CLL.

A Rare Case of Collision Tumours of the Ovary: An Ovarian Serous Cystadenoma Coexisting with Fibrothecoma

The incidence of epithelial tumours of the ovary ranges from 9-17 per 100,000 and is the highest in high-income countries, with the exception of the Japan. The coexistence of neoplastic Müllerian epithelial and sex cord-stromal elements within a single tumour is extremely rare. We describe the case of a 74-year-old woman with a voluminous left adnexal formation. Pre-operative assessment with ultrasound evaluation made a suspicious diagnosis of benignity of the lesion. Bilateral salpingo-ovariectomy was performed. Intraoperative frozen section analysis results in the diagnosis of fibrothecoma in the context of serous cystadenoma. The diagnosis is confirmed by histological examination. Some authors suggest labelling this phenomenon as collision tumours.

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.

Papillary and Medullary Thyroid Carcinomas Presenting as Collision Tumors: A Case Series of 21 Cases at a Tertiary Care Cancer Center

Collision tumor is the occurrence of two histologically and morphologically distinct tumors within the same organ with no histological admixture. Collision tumors of the thyroid are extremely rare constituting < 1% of all thyroid tumors. Clinical profiles and pathological features of Medullary thyroid carcinoma (MTC) and Papillary thyroid carcinoma (PTC) presenting as Collision tumors of thyroid, diagnosed between 2009 and 2019, at a tertiary care cancer center were retrospectively analyzed. Collision tumors comprised 4.7% of all MTC cases diagnosed over 10 years. A total of 21 cases (11males, 11 females, M:F = 1) were retrieved with the mean age of patients being 45.33 years (range 26-77 years). More than half of PTCs involved the right lobe of the thyroid (66.6%). About half (53.4%) of MTCs affected the left lobe. Imaging done pre-operatively failed to identify the smaller second tumor in 60% of the cases with both tumours in separate lobes. Pre-operative FNAC showed only MTC in all 8 cases in which it was done. Papillary microcarcinoma (m-PTC) was seen in 85.7% cases, with one case of multifocal m-PTC. MTC (mean size 3.12 cm), on an average, was 3 times larger than the PTC (mean size 0.91 cm). The histological variants of MTC included-oncocytic (1/21, 4.7%), spindle cell (1/21, 4.7%), epithelial (3/21, 14.2%) and classical (16/21, 76.2%) and of PTC included classic PTC (12/21, 57.14%), Hurthle cell (2/21, 9.52%), tall cell (1/21, 4.76%) and follicular variant of PTC (6/21, 28.57%). The microscopic extrathyroidal extension (ETE) due to MTC and PTC component was 42.8% and 9.5% respectively. Lymph node metastasis was seen in 16 (76.2%) cases; 87.5% (14/16) of which were contributed by MTC, 12.5% (2/16) by PTC alone, and 12.5% (2/16) cases showed metastasis from both MTC and PTC. MTC had a higher stage than PTC in 85.5% of cases. Collision tumors of the thyroid are exceedingly rare, and possibly underdiagnosed due to variation in sampling techniques, especially of the grossly "normal lobe". The low incidence in our cohort is in favor of the "Chance theory" of co-occurrence. This diagnosis is important due to its therapeutic and prognostic implications.

Collision carcinoma of squamous cell carcinoma and small cell neuroendocrine carcinoma of the larynx: A case report and review of the literature

BACKGROUND

Collision carcinoma is rare in clinical practice, especially in the head and neck region. In this paper, we report a case of squamous cell carcinoma (SCC) and neuroendocrine carcinoma (NEC) colliding in the larynx and review 12 cases of collision carcinoma in the head and neck to further understand collision carcinoma, including its definition, diagnosis, and treatment.

CASE SUMMARY

A 61-year-old man presented with a 1-year history of hoarseness. Contrast-enhanced magnetic resonance imaging of the larynx revealed that the right vocal cord had a nodule-like thickening with obvious enhancement. Laryngoscopy revealed a neoplasm on the right vocal cord, and a malignant tumor was initially considered. A frozen section of right vocal cord was performed under general anesthesia. The pathological result showed a malignant tumor in the right vocal cord. The tumor was excised with a CO₂ laser (V_c type). Routine postoperative pathology showed moderately differentiated SCC with small cell NEC in the right vocal cord. No metastatic lymph nodes or distant metastases were found on postoperative positron emission tomography/computed tomography. Because of the coexistence of SCC and NEC, the patient received adjuvant chemotherapy and radiotherapy. The patient was followed for 8 mo, and no recurrence or distant metastasis was found.

CONCLUSION

The treatment of collision carcinoma in the head and neck region is uncertain due to the small number of cases.

Ovarian collision tumors: imaging findings, pathological characteristics, diagnosis, and differential diagnosis

Collision tumors are uncommon neoplasms in which elements of differing histologic origins coexist in a single mass. Ovarian collision tumors are a rare subtype of such lesions. The identification of collision tumors by radiologic examinations is essential to ensure that comprehensive biopsies are performed to guide appropriate treatments. According to the clinical and imaging findings of 12 patients and reviews of previous studies, ovarian collision tumors are mixtures of different combinations of epithelial tumors, germ cell tumors, and sex-cord-stromal tumors. The smaller tumors are usually located inside ("nested tumor") or on the wall ("back to back") of the larger tumors. Each type of ovarian collision tumors presents specific CT/MRI features in accordance with their histologic origins and collision patterns. Knowledge of the imaging features of ovarian collision tumors is crucial to aid preoperative diagnostic accuracy.

Primary Squamous Cell Carcinoma of Trachea Arising 4 Years After Radioiodine Treatment of Papillary Carcinoma of Thyroid

Primary squamous cell carcinoma (SCC) of the trachea is rare. Here, we presented a rare case of primary SCC of the trachea arising 4 years after radioiodine (RAI) treatment of papillary carcinoma of the thyroid. In this case, concomitant uptake of I-RAI and F-FDG was demonstrated in the thyroidal mass with tracheal invasion, which mimicked mixed well-differentiated and dedifferentiated thyroid carcinoma. The diagnosis of SCC of the trachea was made only after tracheal biopsy. This case illustrates that FDG-avid thyroid bed lesion, in the presence of thyroid carcinoma, may not necessarily be related to the thyroid pathology.

A novel BAP1 mutation is associated with melanocytic neoplasms and thyroid cancer

Germline mutations in the tumor suppressor gene, BRCA-1 associated protein (BAP1), underlie a tumor predisposition syndrome characterized by increased risk for numerous cancers including uveal melanoma, melanocytic tumors and mesothelioma, among others. In the present study we report the identification of a novel germline BAP1 mutation, c.1777C>T, which produces a truncated BAP1 protein product and segregates with cancer. Family members with this mutation demonstrated a primary clinical phenotype of autosomal dominant, early-onset melanocytic neoplasms with immunohistochemistry (IHC) of these tumors demonstrating lack of BAP1 protein expression. In addition, family members harboring the BAP1 c.1777C>T germline mutation developed other neoplastic disease including thyroid cancer. IHC analysis of the thyroid cancer, as well, demonstrated loss of BAP1 protein expression. Our investigation identifies a new BAP1 mutation, further highlights the relevance of BAP1 as a clinically important tumor suppressor gene, and broadens the range of cancers associated with BAP1 inactivation. Further study will be required to understand the full scope of BAP1-associated neoplastic disease.

Collision tumors of the thyroid: A case report and review of the literature

BACKGROUND

Collision tumors of the thyroid are a rare pathology that present a diagnostic and treatment challenge. In this report, we present an interesting case and a review of the current literature as to inform management.

METHODS AND RESULTS

An 88-year-old woman presented with acute airway compromise and vocal cord paralysis. CT identified a thyroid mass and widespread metastasis. Histopathology identified the lesion as a collision tumor consisting of a squamous cell carcinoma (SCC) and papillary thyroid carcinoma. The patient was managed with surgery and palliative radiotherapy. However, she died from complications of a lower respiratory tract infection. We also present a review of the literature with 33 cases reviewed.

CONCLUSION

Management of collision tumors is complex because of the duality of the pathology. They should be managed in a multidisciplinary team setting and treatment should be patient specific. Generally, the most aggressive neoplasm should guide treatment. We recommend surgical management with adjunct therapy.

Preoperative Evaluation of Thyroid Epithelial Lesions by DNA Ploidy and Galectin-3 Expression in FNAC

AIM: This study aimed to investigate the value of DNA ploidy and galectins-3 immunostain in the preoperative evaluation of thyroid epithelial lesions.MATERIAL AND METHODS: Sixty patients presenting with thyroid enlargement were included in this study and referred by clinicians for FNA. Routine cytological evaluation was done on PAP   stained slides according to the WHO criteria and at least three slides were prepared for routine cytological examinations. The nuclear DNA analysis was performed at the Pathology Department, National Research Center using the Leica Qwin 500 Image Analyzer (LEICA Imaging Systems Ltd, Cambridge, England). Galectin-3 expression was investigated in all tissues using streptavidin-biotin technique.RESULTS: Conventional Fine needle aspiration cytology (FNAC) of 60 cases could diagnose malignancy with a sensitivity of 60%, negative predictive value (NPV) 71.4%, and overall diagnostic accuracy of 80%. The aneuploidy was significantly associated with malignancy, with sensitivity 90.9%, specificity 83.3% and accuracy 88.3%. On using galectin-3 immunocytochemichal stain on cell blocks prepared from FNA the values were improved, sensitivity 93.3% specificity 86.7% and overall accuracy 90% and it was noticed that galectin-3 over expression was significantly associated with malignancy.CONCLUSIONS: From the results of this study we can consider that DNA ploidy and Galectin-3 could refine the FNA results and  increase its sensitivity as a screening test from sensitivity(60%) to reach sensitivity (93.3%), thus decreasing the false negative cases. From this study, it is concluded that the application of ancillary techniques as galectin-3 immunocytochemical markers may become a reliable indicator for surgical intervention, DNA ploidy measurements on the other hand may be of value in galectin-3 negative cases to determine the behavior of the lesion in such cases & refine the preoperative assessment by out ruling false negative cases.

Retroperitoneal schwannoma with monoclonal plasma cell infiltration: an exceptionally rare collision tumor?

Collision tumors within the retroperitoneum are rare. We present the case of a 54-year-old man with an incidental finding of a well-defined iliopsoas mass. He underwent marginal resection via an anterior superior ilio-inguinal approach. Histological examination revealed typical features of a schwannoma surrounded by a notable plasma cell infiltrate. On immunohistochemistry stains, the spindled cells displayed diffuse, strong nuclear and cytoplasmic positivity for S100, whereas epithelial membrane antigen, glial fibrillary acidic protein, and neurofilament stains were uniformly negative. The plasma cell infiltrate was diffusely positive for CD 138, with a majority of them demonstrating positive staining for lambda light chain and negative for kappa light chain. Hematological review found no evidence of marrow plasmacytosis and multiple myeloma was ruled out. At 12 month follow-up, the patient remains free of any recurrence. To our knowledge this is the second case of a schwannoma coexisting with a monoclonal plasma cell infiltrate and the first in the retroperitoneum.

SCF(β-TRCP) suppresses angiogenesis and thyroid cancer cell migration by promoting ubiquitination and destruction of VEGF receptor 2

The E3 ubiquitin ligase β-TRCP, acting in concert with casein kinase I, drives ubiquitination and degradation of VEGFR2, and renders human papillary thyroid cancer cells resistant to the VEGFR2 inhibitor sorafenib.

The incidence of human papillary thyroid cancer (PTC) is increasing and an aggressive subtype of this disease is resistant to treatment with vascular endothelial growth factor receptor 2 (VEGFR2) inhibitor. VEGFR2 promotes angiogenesis by triggering endothelial cell proliferation and migration. However, the molecular mechanisms governing VEGFR2 stability in vivo remain unknown. Additionally, whether VEGFR2 influences PTC cell migration is not clear. We show that the ubiquitin E3 ligase SCF^β-TRCP promotes ubiquitination and destruction of VEGFR2 in a casein kinase I (CKI)–dependent manner. β-TRCP knockdown or CKI inhibition causes accumulation of VEGFR2, resulting in increased activity of signaling pathways downstream of VEGFR2. β-TRCP–depleted endothelial cells exhibit enhanced migration and angiogenesis in vitro. Furthermore, β-TRCP knockdown increased angiogenesis and vessel branching in zebrafish. Importantly, we found an inverse correlation between β-TRCP protein levels and angiogenesis in PTC. We also show that β-TRCP inhibits cell migration and decreases sensitivity to the VEGFR2 inhibitor sorafenib in poorly differentiated PTC cells. These results provide a new biomarker that may aid a rational use of tyrosine kinase inhibitors to treat refractory PTC.

Follicular and papillary carcinoma: a thyroid collision tumor

The objective of this study was to report a collision tumor of papillary and follicular carcinoma of the thyroid. Case report and review of the literature was studied. A 62 year old female presented with a thyroid mass diagnosed the year prior. Physical exam revealed a 6 × 4 cm predominantly left sided thyroid mass that was confirmed on imaging as well. Thyroid function tests were within normal limits. Ultrasound-guided fine needle aspiration suggested a follicular neoplasm. Consequently, the patient underwent a left hemi-thyroidectomy. The pathology was reported as being collision tumor with a combination of follicular and papillary carcinoma. A completion thyroidectomy was performed followed by post operative radio-iodine therapy. Collision tumors are rare involving two or more histologically distinct neoplastic morphologies separated by normal tissue in one or more organ systems. This is to our knowledge the first report of a collision tumor of the thyroid involving a follicular and papillary carcinoma.

Collision tumor of the thyroid gland: primary squamous cell and papillary thyroid carcinoma

Introduction. Collision tumor of the thyroid gland is defined when independent and histologically distinct tumors coexist within the gland. The presence of both papillary and squamous cell carcinoma in the thyroid gland is unusual. Suggested etiologies include embryonic remanents of squamous epithelium, chronic inflammation, or thyroid malignancies promoting squamous metaplasia. Case Presentation. An elderly patient presented with a rapid enlargement of a long-standing right thyroid nodule. The tumor was locally invasive and unresectable. Pathology revealed the diagnosis of papillary and squamous cell carcinoma of the thyroid gland. Possible primary sites for squamous cell carcinoma in upper aerodigestive tract were excluded. The patient outcome was fatal although palliative chemoradiotherapy. Discussion. Collision tumor of papillary and squamous cell carcinoma of the thyroid gland is a rare entity that may imply bad prognosis, as to the presence of the squamous portion. The best treatment includes resection of the tumor; unfortunately it is not possible in most cases.

Merged histological types of malignant thyroid tumor: experience and controversy

Malignant tumors of the thyroid that consist of merged histological types are a rare clinical entity, with an obscure pathogenesis and no consensus of opinion on nomenclature. Eight patients with merged histological types of thyroid malignant tumor at a single medical center were enrolled between January 1977 and December 2009. These patients were surgically treated and were followed postoperatively from 1 month to 34 years. Preoperative patient characteristics, B-type ultrasonography, computed tomography scan, thyroid function tests, postoperative pathology, immunohistochemistry, and prognosis data were collected. Merged histological types of thyroid malignant tumor accounted for 0.12% of all thyroid malignant tumors treated during this period. Preoperative imageology and laboratory data have no specific value toward diagnosis of merged histological types of thyroid malignant tumor. Merged histological types of thyroid carcinoma that had undergone radical resection in combination with hormonal therapy and I(131) radiotherapy achieved a satisfactory outcome, while other merged thyroid malignant tumors were usually associated with a poor prognosis. Prognosis depended on the highest grade among an individual group of malignant tumors.

Squamous cell carcinoma of the thyroid gland: primary or secondary disease?

OBJECTIVE

To review the aetiopathogenesis, clinical characteristics, immunohistochemical profile, prognosis and treatment options for primary thyroid squamous cell carcinoma, and to compare it with squamous cell carcinoma metastatic to the thyroid, thus providing the reader with a framework for differentiating primary and secondary disease.

METHOD

Review of English language literature from the past 25 years.

SEARCH STRATEGY

A search of the Medline, Embase and Cochrane databases (April 1984 to April 2009) was undertaken to enable a comprehensive review.

RESULTS

After applying strict criteria for the diagnosis of primary thyroid squamous cell carcinoma, 28 articles were identified reporting 84 cases. When reviewing secondary thyroid squamous cell carcinoma, we only analysed cases of squamous cell carcinoma metastatic to the thyroid gland, and found 28 articles reporting 78 cases.

CONCLUSION

It is possible to differentiate between primary and secondary thyroid squamous cell carcinoma, on the basis of combined evidence from clinical examination and endoscopic, pathological and radiological evaluation. Such differentiation is important, as the prognosis for primary squamous cell carcinoma is uniformly poor irrespective of treatment, and the most suitable option may be supportive therapy. Treatment for secondary squamous cell carcinoma of the thyroid varies with the site and extent of spread of the primary tumour.

The occurrence of rare cancers in U.S. adults, 1995-2004

OBJECTIVE

Rare cancers have been traditionally understudied, reducing the progress of research and hindering decisions for patients, physicians, and policy makers. We evaluated the descriptive epidemiology of rare cancers using a large, representative, population-based dataset from cancer registries in the United States.

METHODS

We analyzed more than 9 million adult cancers diagnosed from 1995 to 2004 in 39 states and two metropolitan areas using the Cancer in North America (CINA) dataset, which covers approximately 80% of the U.S. population. We applied an accepted cancer classification scheme and a published definition of rare (i.e., fewer than 15 cases per 100,000 per year). We calculated age-adjusted incidence rates and rare/non-rare incidence rate ratios using SEER*Stat software, with analyses stratified by gender, age, race/ethnicity, and histology.

RESULTS

Sixty of 71 cancer types were rare, accounting for 25% of all adult tumors. Rare cancers occurred with greater relative frequency among those who were younger, nonwhite, and of Hispanic ethnicity than among their older, white, or non-Hispanic counterparts.

CONCLUSIONS

Collectively, rare tumors account for a sizable portion of adult cancers, and disproportionately affect some demographic groups. Maturing population-based cancer surveillance data can be an important source for research on rare cancers, potentially leading to a greater understanding of these cancers and eventually to improved treatment, control, and prevention.

Collision tumor of the thyroid and larynx: a patient with papillary thyroid carcinoma colliding with laryngeal squamous cell carcinoma

BACKGROUND

The term "collision tumor" refers to the coexistence of two histologically distinct malignant tumors within the same mass. Collision tumors involving the thyroid gland and/or neck region are especially uncommon, with most reported cases involving papillary thyroid carcinoma in coexistence with medullary thyroid carcinoma, follicular carcinoma, and metastatic disease, the latter including a rare occurrence of metastatic liposarcoma and thyroid papillary carcinoma. A collision tumor of papillary thyroid carcinoma and squamous cell carcinoma primary to the thyroid has also been reported.

SUMMARY

We now report a collision tumor comprised of well-differentiated papillary thyroid carcinoma and squamous cell carcinoma that originated as a laryngeal primary tumor. Histologically, the thyroid mass is consisted of well-differentiated papillary thyroid carcinoma. The laryngeal mass consisted of in situ and invasive squamous cell carcinoma. Both cancers were extensively infiltrative into the soft tissues of the neck and paraglottic space where the histologically distinct tumor types approximated one another but were not admixed with each other. Additionally, cervical lymph nodes showed metastatic carcinoma, including independent cervical lymph nodes with metastatic squamous cell carcinoma only, cervical lymph nodes with metastatic papillary thyroid carcinoma only, and cervical lymph nodes with foci of both papillary thyroid carcinoma and squamous cell carcinoma.

CONCLUSION

As best we can determine this is the first publication of a collision tumor comprised of a well-differentiated papillary thyroid carcinoma and squamous cell carcinoma that originated as a laryngeal primary tumor. For any patient with a thyroid mass that appears to be in continuity with a laryngeal mass, more commonly one would find invasive thyroid cancer, but one must consider a collision tumor in the differential diagnosis.

Collision tumor: serous cystadenocarcinoma and dermoid cyst in the same ovary

INTRODUCTION

Collision tumor means the coexistence of two adjacent, but histologically distinct tumors without histologic admixture in the same tissue or organ. Collision tumors involving ovaries are extremely rare.

CASE

We present a case of 45-year-old parous woman with a left dermoid cyst, with unusual imaging findings, massive ascites and peritoneal carcinomatosis. The patient underwent cytoreductive surgery. The histopathology revealed a collision tumor consisting of an invasive serous cystadenocarcinoma and a dermoid cyst.