Sciency Thoughts: An osteogenic tumour in a 1.98-million-year-old Australopithicine from Malapa Cave, South Africa.

Neoplasmic tumors are areas of localized tissue growth where cellular proliferation occurs without the oversight of the bodies growth control mechanisms. These are split into two categories, malign growths which are often fatal, and which are the second highest cause of death among modern human populations (after coronary disease), and benign growths, which are not typically lethal but which often cause chronic long-term illnesses. Cancers are often considered to be modern diseases, caused by poor lifestyles choices which make us more prone to the genetic damage that causes them, but they are known in both the fossil and archaeological record, albeit at extremely low levels, and probably occurred at higher levels than we are aware of, as only cancers affecting hard tissues such as bone are likely to be preserved.

In a paper published in the South African Journal of Science on 28 July 2016, Patrick Randolph-Quinney of the School of Anatomical Sciences and Evolutionary Studies Institute at the University of theWitwatersrand, describe a benign tumour from a 1.98-million-year-old Australopithicine from Malapa Cave at the Cradle of Humankind WorldHeritage Site in Guateng Province, South Africa.

The tumour is located in the sixth thoracic vertebra of an individual known as MH1 (Malapa Hominin 1), a juvenile male with a development roughly equivalent of a 12-13-year-old Modern Human, which is the specimen from which the species Australopithecus sediba (thought to bebe a likely candidate for the species ancestral to the genus Homo) was described. This specimen is one of two specimens of Australopithecus sediba from Malapa Cave, which, along with a number of other Hominins, are thought to have fallen into the vertical cave and died, rather than used it as a dwelling, as with the other caves at the Cradle of Humankind site.

The tumour measures approximately 6.7 by 5.9 mm and penetrates the bone from the right surface of the bone. The right portion of the vertebrae appears thickened relative to the left, apparently indicating remodelling of the bone in reaction to the tumour. The lesson formed by the tumour widens beneath the entrance hole, then narrows deeper into the bone, deviating slightly to the right. It does not penetrate the vertebral canal, but the position of and bone modification caused by the tumour may have affected the articulation of both the spine and the right shoulder, and could quite possibly have been a source of acute or chronic pain and even muscle spasming.

Sixth thoracic vertebra of juvenile Australopithecus sediba (Malapa Hominin 1). Partially transparent image volume with the segmented boundaries of the lesion rendered solid pink. Volume data derived from phase-contrast X-ray synchrotron microtomography. (a) Left lateral view, (b) superior view, (c) right lateral view. Paul Tafforeau in Randolph-Quinney et al. (2016).

Given the thickening of the bone around the lesson, Randolph-Quinney et al. rule out the possibility of this being a post-mortem artefact. The absence of inflammation around the the tumour is also indicative; as such inflammation would be expected with cancers such as brucellosis, nonspecific osteitis, haematogenous osteomyelitis or treponemal osteitis, and the morphology of the tumour is inconsistent with a diagnosis of vertebral osteomyelitis. There is no sign of the deformation and regrowth that might be associated with a trauma such as a healed fracture, and the youth of the victim makes it highly unlikely that the lesson was caused by osteosarcoma, chondrosarcoma or Ewing’s sarcoma.

The possible causes of the lesson are therefore thought to be osteoid osteoma, osteoblastoma, giant cell tumour and aneurysmal bone cyst, of which an osteoid osteoma or osteoblastoma are thought to be the most likely. Of these the pathology most resembles an osteoid osteoma, though these are rare in the bones of the spine, being most common in the lower limb bones. Randolph-Quinney et al. therefore conclude that an osteoid osteoma os the most likely cause of the observed pathology, but that an osteoblastoma cannot be ruled out.

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Monday, 19 September 2016

An osteogenic tumour in a 1.98-million-year-old Australopithicine from Malapa Cave, South Africa.